Inhibiting dendrites formation and side-reactions is a critical challenge for practical application of aqueous Zn-ion batteries(AZIBs).Electrolyte additives offer an effective solution to address this problem.Inspired...Inhibiting dendrites formation and side-reactions is a critical challenge for practical application of aqueous Zn-ion batteries(AZIBs).Electrolyte additives offer an effective solution to address this problem.Inspired by using green corrosion inhibitor for metals,we introduce caffeine,extracted from tea-leaf,as an additive to achieve stable AZIBs.Caffeine,with its N and O containing groups,strongly adsorbs on the Zn anode and Zn^(2+)ions.This featured adsorption induces the replacement of water molecules from electric double layer(EDL)and solvation shell,suppressing side-reactions such as corrosion and hydrogen evolution reaction(HER).Moreover,the selective adsorption and steric hindrance of caffeine promote Zn(002)-oriented deposition,resulting in uniform and compact zinc deposits at both low and high current density and areal capacity.Due to the significantly suppressed dendrites and corrosion,the Coulomb Efficiency(CE)reaches 99.24%after 800 cycles,and the Zn||MnO_(2)battery shows a specific capacity of 167.2 mAh g^(−1)with 81%capacity retention after 1000 cycles at 2 A g^(−1).展开更多
By combining the effective Hamiltonian approach and direct ab initio computation, we obtain the phase diagram of SnTiO3with respect to epitaxial strain and temperature. This demonstrates the complex features of the ph...By combining the effective Hamiltonian approach and direct ab initio computation, we obtain the phase diagram of SnTiO3with respect to epitaxial strain and temperature. This demonstrates the complex features of the phase diagram and provides an insight into this system, which is a presumably simple perovskite. Two triple points, as shown in the phase diagram, may be exploited to achieve high-performance piezoelectric effects. Despite the inclusion of the degree of freedom related to oxygen octahedron tilting, the ferroelectric displacements dominate the structural phases over the whole misfit strain range. Finally, we show that SnTiO3can change from hard to soft ferroelectrics with the epitaxial strain.展开更多
Owing to the strong neutron absorption of 151Eu,151Eu free 153EuMnO3-δhas been synthesized to collect the neutron diffraction data for analyzing the magnetic structure of EuMnO3-δ.The obtained neutron diffraction da...Owing to the strong neutron absorption of 151Eu,151Eu free 153EuMnO3-δhas been synthesized to collect the neutron diffraction data for analyzing the magnetic structure of EuMnO3-δ.The obtained neutron diffraction data of 153EuMnO3-δindicates that the magnetic diffraction peaks corresponding to cAAFM(canted A-type antiferromagnetic)phase can be observed,but the magnetic diffraction peaks corresponding to expected ICAFM(incommensurate antiferromagnetic)phase may be too weak to be observed.展开更多
Lead-free dielectric relaxor ferroelectric(RFE)ceramics are one of the promising materials for dielectric energy storage applications.However,the contradiction between high polarization and low hysteresis leads to int...Lead-free dielectric relaxor ferroelectric(RFE)ceramics are one of the promising materials for dielectric energy storage applications.However,the contradiction between high polarization and low hysteresis leads to interior energy storage performance,which greatly limits their applications in high/pulsed power systems.Here,we propose an effective strategy to significantly improve the energy storage properties of 0.94Bi_(0.5)Na_(0.5)TiO_(3)-0.06BaTiO_(3)(0.94BNT-0.06BT)with a morphotropic phase boundary(MPB)composition by constructing multiscale polymorphic domains and local heterogeneous structures.The introduction of Nd(Mg_(1/2)Hf_(1/2))O_(3)(NMH)facilitates the formation of short-range ordered polar nanoregions(PNRs).Moreover,small amounts of nanodomains with high polarization are resulted from local heterogeneous structures with Bi-and Ti-rich regions.Multiscale polymorphic domains with the coexistence of rhombohedral/tetragonal(R+T)nanodomains and PNRs ensure both high polarization and low hysteresis,which is crucial for improving the energy storage performance.Furthermore,the excellent electrical insulation is resulted from the high insulation resistivity,grain size at the submicron scale and a wide band gap by NMH doping.Therefore,a high recoverable energy density(Wrec)of 7.82 J/cm^(3) with an ultrahigh efficiency(η)of 93.1%is realized in the designed BNT-BT-NMH ternary system because of both a largeΔP and high Eb.These findings,together with good temperature/frequency/cycling stability,indicate that the optimum composition ceramics are very promising materials for energy storage applications in high/pulsed power systems.展开更多
Aurivillius phase CaBi_(2)Nb_(2)O_(9)(CBNO)ceramic with an ultrahigh Curie temperature(TC)of∼934℃shows huge potential in high-temperature piezoelectric applications.However,low piezoelectricity and poor electric ins...Aurivillius phase CaBi_(2)Nb_(2)O_(9)(CBNO)ceramic with an ultrahigh Curie temperature(TC)of∼934℃shows huge potential in high-temperature piezoelectric applications.However,low piezoelectricity and poor electric insulation prevent its applications in high-temperature sensing.Here,we propose an effective multi-field coupling strategy to synergistically optimize piezoelectric property,electrical conduction behavior and temperature stability of CBNO ceramic.The constructed lattice stress and electric fields induced by introducing Li/Pr and Bi/Sc doping have great impacts on the lattice structure,microstructure,domain structure and defect chemistry.Therefore,a significant increase in piezoelectric activity(d_(33))is resulted from the enhancement of polarization,the improvement of breakdown electric field and the production of nanoscale domains.In especial,the existence of pseudo-tetragonal phase boundary is helpful for the enhanced d_(33).In the designed Ca_(1-3x)(Li_(0.5)Pr_(0.5))_(x)Bi_(2+2x)Nb_(2-x)Sc_(x)O_(9)system,a high d_(33)of∼18.2 pC/N accompanied by an ultrahigh TC of∼938℃is achieved in the x=0.02 ceramic.This combined with high electrical resistivity(ρ∼1.72 MΩ⋅cm at 600℃)and nearly stable d_(33)(up to 800℃)indicates that it is a very promising piezoelectric material for high-temperature(up to 600℃or higher)sensing applications.展开更多
The electrocaloric effect(ECE)offers a pathway to environmentally sustainable and easily miniaturized refrigeration technology,positioning it as a front-runner for the next generation of solid-state cooling solutions....The electrocaloric effect(ECE)offers a pathway to environmentally sustainable and easily miniaturized refrigeration technology,positioning it as a front-runner for the next generation of solid-state cooling solutions.This research unveils a remarkable ECE in afinely tuned(Ba_(0.86)Ca_(0.14))_(0.98)La_(0.02)Ti_(0.92)Sn_(0.08)O_(3)ceramic,exhibiting a temperature shift(DT)of 1.6 K across more than 85%of the maximumΔT(ΔT_(max))and spanning an exceptionally wide operational range of 92 K.Our investigation on dielectric responses and ferroelectric polarization-electricfield(PeE)loops suggests that the broad operational scope results from the fragmentation of extended ferroelectric domains into smaller domains and polar nano-regions(PNRs)supported by PFM analysis.Furthermore,the introduction of La enhances spontaneous polarization by significantly extending the maximum electricfield that can be applied,facilitating highperformance ECE at ambient temperature.This study positions BaTiO_(3)-based lead-free ceramic as a sustainable alternative for addressing the cooling demands of modern electronic components,marking a significant stride toward next-generation solid-state refrigeration.展开更多
Uniform deposition is a promising strategy to inhibit dendrite growth and corrosion of the Zn anode in cost-effective energy storage systems:aqueous Zn-ion batteries(AZIBs).Herein,we report a regulating Zn^(2+)ions di...Uniform deposition is a promising strategy to inhibit dendrite growth and corrosion of the Zn anode in cost-effective energy storage systems:aqueous Zn-ion batteries(AZIBs).Herein,we report a regulating Zn^(2+)ions dissolution/deposition method for achieving a highly reversible Zn anode.11-mercaptoundecanoic acid(MUA)as ligands was utilized to protect the(002)plane,benefiting from the strong affinity between the thiol group and Zn,with MUA anchoring in the form of Zn-S-RCOOH,which contributes to a stable interface for uniform deposition/deposition.展开更多
Ferroelectric materials are highly promising for next-generation electro-optic(EO)modulators because of their ultrafast and efficient light modulation.However,efforts to maximize polarization freedom for large refract...Ferroelectric materials are highly promising for next-generation electro-optic(EO)modulators because of their ultrafast and efficient light modulation.However,efforts to maximize polarization freedom for large refractive index modulation—through domain engineering,epitaxial strain,and defect engineering—have hit limitations,leaving intrinsic polarization mechanisms largely unexplored.Here,we report a giant effective EO coefficient(~233.5 pm/V)in PbZr_(0.52)Ti_(0.48)O_(3)(PZT)films,which surpasses all reported values measured under an in-plane electric field and significantly exceeds the theoretical limit(~13 pm/V)as well as the value of LiNbO_(3)(~31 pm/V).Beyond conventional domain switching,phase transitions and domain wall variations critically enhance the EO effect.The highly relaxed structure of the PZT film,with mixed[001]and[100]orientations and disordered nanoscale phases,enables unprecedented polarization control.This unique configuration breaks the theoretical EO coefficient limit,bridging the gap between predictions and experimental results.Owing to its high Curie temperature and compatibility with wafer-scale fabrication,PZT has emerged as a promising candidate for next-generation high-performance EO modulators.Our findings not only advance the frontiers of ferroelectric EO materials but also pave the way for exploring other ferroelectric thin-film devices,such as those for energy storage and electrocaloric cooling,by leveraging enhanced polarization modulation mechanisms.展开更多
Both sustainable development in environment and safety of high-power systems require to develop a novel lead-free dielectric capacitor with high energy density(Wrec)at low applied electric field.In this work,a remarka...Both sustainable development in environment and safety of high-power systems require to develop a novel lead-free dielectric capacitor with high energy density(Wrec)at low applied electric field.In this work,a remarkably high Wrec of 2.9 J/cm^(3) accompanying with energy storage efficiency of 56% was achieved in Ag_(0.9)Sr_(0.05)NbO_(3) ceramic at a low applied electric field of 190 kV/cm,by improving antiferroelectricity and introducing relaxor behaviour.The improved anti-ferroelectric stability was attributed to the decreased tolerance factor and average electronegativity difference,while the relaxor behaviour was associated with the increased disordered local structure by Sr-doping.Moreover,the Ag_(0.9)Sr_(0.05)NbO_(3) ceramics also exhibited outstanding temperature stability in energy density with small variation less than 5% over 20-140℃.The results indicate that the Ag_(0.9)Sr_(0.05)NbO_(3) ceramic is a promising candidate for low-electric-field driving capacitors.展开更多
The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage den...The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage density and efficiency. Herein, good energy storage properties were realized in (1-x)NaNbO_(3)- xNaTaO_(3) ceramics, by building a new phase boundary. As a result, a high recoverable energy density(Wrec) of 2.2 J/cm3 and efficiency (h) of 80.1% were achieved in 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic at300 kV/cm. The excellent energy storage performance originates from an antiferroelectric-paraelectricphase boundary with simultaneously high polarization and low hysteresis, by tailoring the ratio ofantiferroelectric and paraelectric phases. Moreover, the 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic also exhibitedgood temperature and frequency stability, together with excellent charge-discharge performance. Theresults pave a good way of designing new NaNbO_(3)-based antiferroelectrics with good energy storageperformance.展开更多
(1-x)K_(0.5)Na_(0.5)Nb0_(3-x)Bi(Zn_(2/3)Nb_(1/3))0_(3)((1-x)KNN-xBZN,x=0.010,0.015,0.020,0.025,and 0.030)lead-free ceramics were fabricated via a traditional solid-state method.The crystal structure,microstructure,die...(1-x)K_(0.5)Na_(0.5)Nb0_(3-x)Bi(Zn_(2/3)Nb_(1/3))0_(3)((1-x)KNN-xBZN,x=0.010,0.015,0.020,0.025,and 0.030)lead-free ceramics were fabricated via a traditional solid-state method.The crystal structure,microstructure,dielectric,and conductivity behavior of this system were studied.Combined with X-ray diffraction(XRD)patterns,Rietveld refinement,and dielectric spectroscopy,an orthorhombic phase was determined for x=0.010,an orthorhombic-tetragonal mixed phase was identified for x=0.015,and a rhombohedral symmetry appears in 0.020≤x≤0.030.Both 0.98KNN-0.02BZN and 0.975KNN-0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent(tan)in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic.The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly,then drop sharply,and finally decline slowly,which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.展开更多
A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permitt...A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permittivity(εr)9.43,a quality factor(Q×f)of 20,000 GHz,and a temperature coefficient of resonance frequency(τf)-76 ppm/℃.To get a deep understanding of the relationship between composition,structure,and dielectric performances,magnesium substitution for copper in Ba2CuGe2O7 was conducted.Influences of magnesium doping on the sintering behavior,crystal structure,and microwave dielectric properties were studied.Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure,grain morphology,and size distribution,while induced visible variation in the local structure as revealed by Raman analysis.Microwave dielectric properties exhibit a remarkable dependence on composition.On increasing the magnesium content,the relative permittivity featured a continuous decrease,while both the quality factor and the temperature coefficient of resonance frequency increased monotonously.Such variations in dielectric performances were clarified in terms of the polarizability,packing fraction,and band valence theory.展开更多
(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferr...(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferroelectric features,among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value Suni¼0.51%at electric field of 65 kV/cm,with high piezoelectric stain coefficient d33*of 890 pm/V at 45 kV/cm,while the non-ergodic compositions present unrepeatable large strain response.Based on the electric field-composition phase diagram,the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition.In addition,the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions.This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties.展开更多
Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion conductivity.The inherent structural characteristics are urgent to be resolved due to its particular...Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion conductivity.The inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis process.Herein,a thorough study of the temperature-dependent neutron,X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine BNT.Phase transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature,associated with well saturated ferroelectric states.Significant structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures,focusing on the subtle distortions of ionic displacements,oxygen octahedral tilts and local chemical environments for oxygen vacancies.The ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder,and is strongly affected by the dopant concentration.Together with the lone pair substitution concept,superior oxide ionic conductivity is achieved,and an alternative strategy is provided in designing BNT based oxide ion conductors.展开更多
Fibrosis is a common problem in soft tissue regeneration,often caused by the differentiation of fibroblasts into myofibro-blasts.Because of the nanoscale topology that regulates the mechanical transduction of cells,na...Fibrosis is a common problem in soft tissue regeneration,often caused by the differentiation of fibroblasts into myofibro-blasts.Because of the nanoscale topology that regulates the mechanical transduction of cells,nanofibers or nanoparticles are commonly used to modulate fibroblast differentiation.However,the strength of nanofibers is insufficient,and the physi-ological toxicity of nanoparticles still remains to be verified.In this study,self-induced crystallization was used to construct nano-protrusions on the random and aligned polycaprolactone microfibers to regulate the behavior of fibroblasts.The results revealed that the mechanical properties of microfibers with a nanoscale topology were improved.Immunofluorescence staining manifested that nano-protrusions impeded the activation of integrins and vinculins,thereby inhibiting the nuclear transfer of Yes-associated protein,resulting in a decrease in the expression ofα-smooth muscle actin.Nanoscale topology of microfibers hampered the activation of the Rho/ROCK signalling pathway.In general,we used a simple process to con-struct a fibrous scaffold with a micro-nano multilevel structure.This structure can hinder the transformation of fibroblasts into myofibroblasts on both random and aligned fibers,which is expected to prevent fibrosis.展开更多
AB_(2)O_(4)-type spinels with low relative permittivity(ε_(τ))and high quality factor(Q×f)are crucial to high-speed signal propagation systems.In this work,Zn^(2+)/Ge^(4+) co-doping to substitute Ga in ZnGa_(2)...AB_(2)O_(4)-type spinels with low relative permittivity(ε_(τ))and high quality factor(Q×f)are crucial to high-speed signal propagation systems.In this work,Zn^(2+)/Ge^(4+) co-doping to substitute Ga in ZnGa_(2)O_(4) was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously.Zn_(1+2)Ga_(2-2x)Ge_(x)O_(4)(0.1≤x≤0.5)ceramics were synthesised by the conventional solid state method.Zn^(2+)/Ge^(4+) co-substitution induced minimal variation in the macroscopical spinel structure,which effectively lowered the sintering temperature from 1385 to 1250℃.All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties.The compositional dependent quality factor was related to the microstructural variation,being confirmed by Raman features.A composition with x=0.3 shows the best dielectric properties with ε_(τ) ≈10.09,Q×f≈112,700 THz,and ε_(τ) ≈-75.6 ppm/℃.The negative τf value was further adjusted to be near-zero through the formation of composite ceramics with TiO_(2).展开更多
Layered alkali-containing 3d transition-metal oxides are of the utmost importance in the use of electrode materials for advanced energy storage applications such as Li-,Na-,or K-ion batteries.A significant challenge i...Layered alkali-containing 3d transition-metal oxides are of the utmost importance in the use of electrode materials for advanced energy storage applications such as Li-,Na-,or K-ion batteries.A significant challenge in the field of materials chemistry is understanding the dynamics of the chemical reactions between alkali-free precursors and alkali species during the synthesis of these compounds.In this study,in situ high-resolution synchrotron-based X-ray diffraction was applied to reveal the Li/Na/K-ion insertion-induced structural transformation mechanism during high-temperature solid-state reaction.The in situ diffraction results demonstrate that the chemical reaction pathway strongly depends on the alkali-free precursor type,which is a structural matrix enabling phase transi-tions.Quantitative phase analysis identifies for the first time the decomposition of lithium sources as the most critical factor for the formation of metastable intermediates or impurities during the entire process of Li-rich layered Li[Li_(0.2)Ni_(0.2)Mn_(0.6)]O_(2) formation.Since the alkali ions have different ionic radii,Na/K ions tend to be located on prismatic sites in the defective layered structure(Na_(2/3-x)[Ni_(0.25)Mn_(0.75)]O_(2) or K_(2/3-x)[Ni_(0.25)Mn_(0.75)]O_(2))during calcination,whereas the Li ions prefer to be localized on the tetrahedral and/or octahedral sites,forming O-type structures.展开更多
High-entropy effect is a novel design strategy to optimize properties and explore novel materials.In this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were succ...High-entropy effect is a novel design strategy to optimize properties and explore novel materials.In this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature(S.T.)range of 1210–1290℃via a solid-phase reaction route,and medium-entropy(La_(1/3)Nd_(1/3)Sm_(1/3))NbO_(4) and(La_(1/4)Nd_(1/4)Sm_(1/4)Ho_(1/4))NbO_(4)(3RNO and 4RNO)ceramics were compared.The effects of the entropy(S)on crystal structure,phase transition,and dielectric performance were evaluated.The entropy increase yields a significant increase in a phase transition temperature(from monoclinic fergusonite to tetragonal scheelite structure).Optimal microwave dielectric properties were achieved in the high-entropy ceramics(5RNO)at the sintering temperature of 1270℃for 4 h with a relative density of 98.2%and microwave dielectric properties of dielectric permittirity(ε_(r))=19.48,quality factor(Q×f)=47,770 GHz,and resonant frequency temperature coefficient(τ_(f))=–13.50 ppm/℃.This work opens an avenue for the exploration of novel microwave dielectric material and property optimization via entropy engineering.展开更多
Ferroelectric thin/thick films with large electrocaloric(EC)effect are critical for solid state cooling technologies.Here,large positive EC effects with two EC peaks in a broad temperature range(~100 K)were obtained i...Ferroelectric thin/thick films with large electrocaloric(EC)effect are critical for solid state cooling technologies.Here,large positive EC effects with two EC peaks in a broad temperature range(~100 K)were obtained in 0.95Pb_(0.92)La_(0.08)(Zr_(0.70)Ti_(0.30))_(0.98)O_(3)-0.05BiFeO_(3)(BFO-La-codoped PZT)epitaxial thin films deposited on the(100),(110)and(111)oriented SrTiO_(3)(STO)substrates by a sol-gel method.The thin film deposited on the(111)oriented STO substrate exhibited a stronger EC effect(~20.6 K at 1956 kV/cm)near room temperature.However,the thin films deposited on the(100)and(110)oriented STO substrates exhibited a stronger EC effect(~18.8 K at 1852 kV/cm and~20.8 K at 1230 kV/cm,respectively)around the peak of the dielectric permittivity(T_(m),~375 K).Particularly,as the direction of the applied electric field was switched(E<0),the DT of the(100)-oriented thin films around T_(m) was enhanced significantly from 18.8 K to 38.1 K.The self-induced-poling during the preparing process maybe plays a key role on the magic phenomenon.It can be concluded that the BFO-La-codoped PZT epitaxial thin films are promising candidates for application in the next solid-state cooling devices.展开更多
CaCu_(3)Ti_(4-x)Y_(x)O_(12)(0≤x≤0.12)ceramics were fabricated with conventional solid-state reaction method.Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction(XRD)and sca...CaCu_(3)Ti_(4-x)Y_(x)O_(12)(0≤x≤0.12)ceramics were fabricated with conventional solid-state reaction method.Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM),respectively.The impedance and modulus tests both suggested the existence of two different relaxation behavior,which were attributed to bulk and grain boundary response.In addition,the conductivity and dielectric permittivity showed a step-like behavior under 405 K.Meanwhile,frequency independence of dc conduction became dominant when above 405 K.In CCTO ceramic,rare earth element Y^(3+)ions as an acceptor were used to substitute Ti sites,decreasing the concentration of oxygen vacancy around grainelectrode and grain boundary.The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.展开更多
基金supported by the Foundation of Guangxi Innovation Driven Development Project Grant(AA22068080)the Science and Technology Plan of Guangxi(No.ZY22096019,ZY20220101)+1 种基金the National Natural Science Foundation of China(No.52474431)the Research Plan of International Collaboration Fund for Creative Research Teams(ICFCRT)of NSFC(No.W2441008)。
文摘Inhibiting dendrites formation and side-reactions is a critical challenge for practical application of aqueous Zn-ion batteries(AZIBs).Electrolyte additives offer an effective solution to address this problem.Inspired by using green corrosion inhibitor for metals,we introduce caffeine,extracted from tea-leaf,as an additive to achieve stable AZIBs.Caffeine,with its N and O containing groups,strongly adsorbs on the Zn anode and Zn^(2+)ions.This featured adsorption induces the replacement of water molecules from electric double layer(EDL)and solvation shell,suppressing side-reactions such as corrosion and hydrogen evolution reaction(HER).Moreover,the selective adsorption and steric hindrance of caffeine promote Zn(002)-oriented deposition,resulting in uniform and compact zinc deposits at both low and high current density and areal capacity.Due to the significantly suppressed dendrites and corrosion,the Coulomb Efficiency(CE)reaches 99.24%after 800 cycles,and the Zn||MnO_(2)battery shows a specific capacity of 167.2 mAh g^(−1)with 81%capacity retention after 1000 cycles at 2 A g^(−1).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574246,51390472,U1537210,and 11564010)the National Basic Research Program of China(Grant No.2015CB654903)+1 种基金the Natural Science Foundation of Guangxi Zhuang Autonomous Region(Grant Nos.GA139008 and AA138162)the “111” Project of China(Grant No.B14040)
文摘By combining the effective Hamiltonian approach and direct ab initio computation, we obtain the phase diagram of SnTiO3with respect to epitaxial strain and temperature. This demonstrates the complex features of the phase diagram and provides an insight into this system, which is a presumably simple perovskite. Two triple points, as shown in the phase diagram, may be exploited to achieve high-performance piezoelectric effects. Despite the inclusion of the degree of freedom related to oxygen octahedron tilting, the ferroelectric displacements dominate the structural phases over the whole misfit strain range. Finally, we show that SnTiO3can change from hard to soft ferroelectrics with the epitaxial strain.
基金This work is supported by the National Natural Science Foundation of China(Grant 21771007).
文摘Owing to the strong neutron absorption of 151Eu,151Eu free 153EuMnO3-δhas been synthesized to collect the neutron diffraction data for analyzing the magnetic structure of EuMnO3-δ.The obtained neutron diffraction data of 153EuMnO3-δindicates that the magnetic diffraction peaks corresponding to cAAFM(canted A-type antiferromagnetic)phase can be observed,but the magnetic diffraction peaks corresponding to expected ICAFM(incommensurate antiferromagnetic)phase may be too weak to be observed.
基金supported by the National Key R&D Program of China(No.2021YFB3201100)the National Natural Science Foundation of China(Nos.51931004,12264012,52172128 and 52472250)+2 种基金111 Project 2.0(No.BP2018008)the Natural Science Foundation of Guangxi(Nos.AB24010230,AA22068080,and AA23023027)the Science and Technology Plan of Guilin(Nos.2022H03 and ZY20220101).
文摘Lead-free dielectric relaxor ferroelectric(RFE)ceramics are one of the promising materials for dielectric energy storage applications.However,the contradiction between high polarization and low hysteresis leads to interior energy storage performance,which greatly limits their applications in high/pulsed power systems.Here,we propose an effective strategy to significantly improve the energy storage properties of 0.94Bi_(0.5)Na_(0.5)TiO_(3)-0.06BaTiO_(3)(0.94BNT-0.06BT)with a morphotropic phase boundary(MPB)composition by constructing multiscale polymorphic domains and local heterogeneous structures.The introduction of Nd(Mg_(1/2)Hf_(1/2))O_(3)(NMH)facilitates the formation of short-range ordered polar nanoregions(PNRs).Moreover,small amounts of nanodomains with high polarization are resulted from local heterogeneous structures with Bi-and Ti-rich regions.Multiscale polymorphic domains with the coexistence of rhombohedral/tetragonal(R+T)nanodomains and PNRs ensure both high polarization and low hysteresis,which is crucial for improving the energy storage performance.Furthermore,the excellent electrical insulation is resulted from the high insulation resistivity,grain size at the submicron scale and a wide band gap by NMH doping.Therefore,a high recoverable energy density(Wrec)of 7.82 J/cm^(3) with an ultrahigh efficiency(η)of 93.1%is realized in the designed BNT-BT-NMH ternary system because of both a largeΔP and high Eb.These findings,together with good temperature/frequency/cycling stability,indicate that the optimum composition ceramics are very promising materials for energy storage applications in high/pulsed power systems.
基金supported by the National Natural Science Foundation of China(51931004,12264012)and“the Fundamental Research Funds for the Central Universities”supported by the National Natural Science Foundation of China(11974268 and 82327810)111 project 2.0(BP2018008).
文摘Aurivillius phase CaBi_(2)Nb_(2)O_(9)(CBNO)ceramic with an ultrahigh Curie temperature(TC)of∼934℃shows huge potential in high-temperature piezoelectric applications.However,low piezoelectricity and poor electric insulation prevent its applications in high-temperature sensing.Here,we propose an effective multi-field coupling strategy to synergistically optimize piezoelectric property,electrical conduction behavior and temperature stability of CBNO ceramic.The constructed lattice stress and electric fields induced by introducing Li/Pr and Bi/Sc doping have great impacts on the lattice structure,microstructure,domain structure and defect chemistry.Therefore,a significant increase in piezoelectric activity(d_(33))is resulted from the enhancement of polarization,the improvement of breakdown electric field and the production of nanoscale domains.In especial,the existence of pseudo-tetragonal phase boundary is helpful for the enhanced d_(33).In the designed Ca_(1-3x)(Li_(0.5)Pr_(0.5))_(x)Bi_(2+2x)Nb_(2-x)Sc_(x)O_(9)system,a high d_(33)of∼18.2 pC/N accompanied by an ultrahigh TC of∼938℃is achieved in the x=0.02 ceramic.This combined with high electrical resistivity(ρ∼1.72 MΩ⋅cm at 600℃)and nearly stable d_(33)(up to 800℃)indicates that it is a very promising piezoelectric material for high-temperature(up to 600℃or higher)sensing applications.
基金the Science and Technology Plan of Guangxi(Nos.AA23023027,AB24010230)the Key Research and Development Program of Shandong Province(2022CXGC020203)+1 种基金the Natural Science Foundation of China(Grant No.12264012,62271362,12304120)the Science and Technology Plan of Guilin(2022H03 and ZY20220101).
文摘The electrocaloric effect(ECE)offers a pathway to environmentally sustainable and easily miniaturized refrigeration technology,positioning it as a front-runner for the next generation of solid-state cooling solutions.This research unveils a remarkable ECE in afinely tuned(Ba_(0.86)Ca_(0.14))_(0.98)La_(0.02)Ti_(0.92)Sn_(0.08)O_(3)ceramic,exhibiting a temperature shift(DT)of 1.6 K across more than 85%of the maximumΔT(ΔT_(max))and spanning an exceptionally wide operational range of 92 K.Our investigation on dielectric responses and ferroelectric polarization-electricfield(PeE)loops suggests that the broad operational scope results from the fragmentation of extended ferroelectric domains into smaller domains and polar nano-regions(PNRs)supported by PFM analysis.Furthermore,the introduction of La enhances spontaneous polarization by significantly extending the maximum electricfield that can be applied,facilitating highperformance ECE at ambient temperature.This study positions BaTiO_(3)-based lead-free ceramic as a sustainable alternative for addressing the cooling demands of modern electronic components,marking a significant stride toward next-generation solid-state refrigeration.
基金supported by the foundation of Guangxi Innovation Driven Development Project Grant(AA22068080)the Science and Technology Plan of Guangxi(No.ZY22096019)+2 种基金the National Natural Science Foundation of China(No.51874051 and 52111530139)the Australian Research Council Discovery Program(DP220103416)Australian Research Council Future Fel owships(FT200100730,FT210100804)。
文摘Uniform deposition is a promising strategy to inhibit dendrite growth and corrosion of the Zn anode in cost-effective energy storage systems:aqueous Zn-ion batteries(AZIBs).Herein,we report a regulating Zn^(2+)ions dissolution/deposition method for achieving a highly reversible Zn anode.11-mercaptoundecanoic acid(MUA)as ligands was utilized to protect the(002)plane,benefiting from the strong affinity between the thiol group and Zn,with MUA anchoring in the form of Zn-S-RCOOH,which contributes to a stable interface for uniform deposition/deposition.
基金Wen Dong acknowledges National Key R&D Program of China(No.2024YFA1409703)National Natural Science Foundation of China(No.52202134)+4 种基金Hubei Nature Science Foundation(No.2022CFB595)Biaolin Peng acknowledges the Key Research and Development Program of Shandong Province of China(No.2022CXGC020203)National Natural Science Foundation of China(No.62271362)Shenglin Jiang acknowledges National Natural Science Foundation of China(No.61971459)the Analytical and Testing Center of Huazhong University of Science and Technology,Electron Microscopy Center of Yunnan University(No.2022CFB595).
文摘Ferroelectric materials are highly promising for next-generation electro-optic(EO)modulators because of their ultrafast and efficient light modulation.However,efforts to maximize polarization freedom for large refractive index modulation—through domain engineering,epitaxial strain,and defect engineering—have hit limitations,leaving intrinsic polarization mechanisms largely unexplored.Here,we report a giant effective EO coefficient(~233.5 pm/V)in PbZr_(0.52)Ti_(0.48)O_(3)(PZT)films,which surpasses all reported values measured under an in-plane electric field and significantly exceeds the theoretical limit(~13 pm/V)as well as the value of LiNbO_(3)(~31 pm/V).Beyond conventional domain switching,phase transitions and domain wall variations critically enhance the EO effect.The highly relaxed structure of the PZT film,with mixed[001]and[100]orientations and disordered nanoscale phases,enables unprecedented polarization control.This unique configuration breaks the theoretical EO coefficient limit,bridging the gap between predictions and experimental results.Owing to its high Curie temperature and compatibility with wafer-scale fabrication,PZT has emerged as a promising candidate for next-generation high-performance EO modulators.Our findings not only advance the frontiers of ferroelectric EO materials but also pave the way for exploring other ferroelectric thin-film devices,such as those for energy storage and electrocaloric cooling,by leveraging enhanced polarization modulation mechanisms.
基金supported by National Natural Science Foundation of China(Grants 11864004)Guangxi Natural Science Foundation(Grants 2017GXNSFBA198132,2016GXNSFAA380214,2016GXNSFCB380006 and 2017GXNSFFA198015)+2 种基金Science and Technology Major Project of Guangxi,(Grant AA17204100)Innovation Project of Guangxi Graduate Education(Grant YCSW2019053)the funds of the State Key Laboratory of New Ceramics and Fine Processing,Tsinghua University,Beijing(100084),China.
文摘Both sustainable development in environment and safety of high-power systems require to develop a novel lead-free dielectric capacitor with high energy density(Wrec)at low applied electric field.In this work,a remarkably high Wrec of 2.9 J/cm^(3) accompanying with energy storage efficiency of 56% was achieved in Ag_(0.9)Sr_(0.05)NbO_(3) ceramic at a low applied electric field of 190 kV/cm,by improving antiferroelectricity and introducing relaxor behaviour.The improved anti-ferroelectric stability was attributed to the decreased tolerance factor and average electronegativity difference,while the relaxor behaviour was associated with the increased disordered local structure by Sr-doping.Moreover,the Ag_(0.9)Sr_(0.05)NbO_(3) ceramics also exhibited outstanding temperature stability in energy density with small variation less than 5% over 20-140℃.The results indicate that the Ag_(0.9)Sr_(0.05)NbO_(3) ceramic is a promising candidate for low-electric-field driving capacitors.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.11864004 and 52072080)The author also thanks to the fund(Grant No.20KF-16)from the Key Laboratory of New Processing Technology for Nonferrous Metal&Materials,Ministry of Education/Guangxi Key Laboratory of Optical and Electronic Materials and Devices,Guilin University of Technology,Guilin(541004),China.
文摘The NaNbO_(3) antiferroelectrics have been considered as a potential candidate for dielectric capacitorsapplications. However, the high-electric-field-unstable antiferroelectric phase resulted in low energystorage density and efficiency. Herein, good energy storage properties were realized in (1-x)NaNbO_(3)- xNaTaO_(3) ceramics, by building a new phase boundary. As a result, a high recoverable energy density(Wrec) of 2.2 J/cm3 and efficiency (h) of 80.1% were achieved in 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic at300 kV/cm. The excellent energy storage performance originates from an antiferroelectric-paraelectricphase boundary with simultaneously high polarization and low hysteresis, by tailoring the ratio ofantiferroelectric and paraelectric phases. Moreover, the 0.50NaNbO_(3)-0.50NaTaO_(3) ceramic also exhibitedgood temperature and frequency stability, together with excellent charge-discharge performance. Theresults pave a good way of designing new NaNbO_(3)-based antiferroelectrics with good energy storageperformance.
基金supported by the Natural Science Foundation of Guangxi(Grant Nos.2019GXNSFBA245069,AA138162,GA245006,and AA294014)the Middle-aged and Young Teachers’Basic Ability Promotion Project of Guangxi(Grant No.2019KY0290)+3 种基金the Guilin University of Technology(Grant No.GUTQDJJ20176612037)the High Level Innovation Team and Outstanding Scholar Program of Guangxi Institutesthe Open Research Program of Key Laboratory of RF Circuit and System,Ministry of Educationthe Key Laboratory of Large Scale Integrated Design of Zhejiang.
文摘(1-x)K_(0.5)Na_(0.5)Nb0_(3-x)Bi(Zn_(2/3)Nb_(1/3))0_(3)((1-x)KNN-xBZN,x=0.010,0.015,0.020,0.025,and 0.030)lead-free ceramics were fabricated via a traditional solid-state method.The crystal structure,microstructure,dielectric,and conductivity behavior of this system were studied.Combined with X-ray diffraction(XRD)patterns,Rietveld refinement,and dielectric spectroscopy,an orthorhombic phase was determined for x=0.010,an orthorhombic-tetragonal mixed phase was identified for x=0.015,and a rhombohedral symmetry appears in 0.020≤x≤0.030.Both 0.98KNN-0.02BZN and 0.975KNN-0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent(tan)in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic.The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly,then drop sharply,and finally decline slowly,which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.
基金National Natural Science Foundation of China(No.62061011)National Key R&D Program of China(No.2017YFB0406300)+1 种基金Natural Science Foundation of Guangxi Zhuang Autonomous Region(No.2018GXNSFAA281253)high-level innovation team and outstanding scholar program of Guangxi institutes.
文摘A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permittivity(εr)9.43,a quality factor(Q×f)of 20,000 GHz,and a temperature coefficient of resonance frequency(τf)-76 ppm/℃.To get a deep understanding of the relationship between composition,structure,and dielectric performances,magnesium substitution for copper in Ba2CuGe2O7 was conducted.Influences of magnesium doping on the sintering behavior,crystal structure,and microwave dielectric properties were studied.Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure,grain morphology,and size distribution,while induced visible variation in the local structure as revealed by Raman analysis.Microwave dielectric properties exhibit a remarkable dependence on composition.On increasing the magnesium content,the relative permittivity featured a continuous decrease,while both the quality factor and the temperature coefficient of resonance frequency increased monotonously.Such variations in dielectric performances were clarified in terms of the polarizability,packing fraction,and band valence theory.
基金supported by the National Natural Science Foundation of China(51672220,51902258,51972265)Fundamental Research Funds for the Central Universities(3102019GHXM002)+2 种基金State Key Laboratory of Solidification Processing Project(2019-TZ-04)of China,China Postdoctoral Science Foundation(2019M653729)Natural Science Foundation of Shaanxi Province(2019JQ-621)the Shaanxi Province Postdoctoral Science Foundation(2017BSHEDZZ07).
文摘(1-x)(0.8Bi_(1/2)Na_(1/2)TiO3-0.2Bi_(1/2)K_(1/2)TiO3)-xBi(Ni_(2/3)Nb_(1/3))O3(BNKT-xBNN)solid solution ceramics were fabricated by high temperature solid-state reaction method.All the compositions possess relaxor ferroelectric features,among which the ergodic BNKT-0.02BNN exhibits large repeatable electrostrain value Suni¼0.51%at electric field of 65 kV/cm,with high piezoelectric stain coefficient d33*of 890 pm/V at 45 kV/cm,while the non-ergodic compositions present unrepeatable large strain response.Based on the electric field-composition phase diagram,the repeatability of strain response in ergodic compositions can be attributed to the reversible electric-field-induced phase transition.In addition,the effects of BNN contents on the macroscopic strain properties are explored by analyzing the existing states of the polar regions with corresponding thermal evolutions and electric-field-induced phase transitions.This research is expected to guide the design of lead free relaxor ferroelectric materials with desired electrostrain properties.
基金This work was supported by the National Natural Science Foundation(51702249,51602252,51761135118,U1732117)the China Postdoctoral Science Foundation(2017M613065)+2 种基金the Shaanxi Province Science Foundation(2020JQ-751)the Outstanding Youth Science Fund of XUST(2018YQ2-11)The authors thank Shiyanjia Lab for the XPS measurement.
文摘Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3(BNT)ferroelectrics can give rise to considerable oxide-ion conductivity.The inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis process.Herein,a thorough study of the temperature-dependent neutron,X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine BNT.Phase transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature,associated with well saturated ferroelectric states.Significant structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures,focusing on the subtle distortions of ionic displacements,oxygen octahedral tilts and local chemical environments for oxygen vacancies.The ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder,and is strongly affected by the dopant concentration.Together with the lone pair substitution concept,superior oxide ionic conductivity is achieved,and an alternative strategy is provided in designing BNT based oxide ion conductors.
基金Supported by Shanghai Sailing Program(Grant No.20YF1400800)Shanghai Science and Technology Development Fund(21S31900700)111 Project 2.0(Grant no.BP0719035).
文摘Fibrosis is a common problem in soft tissue regeneration,often caused by the differentiation of fibroblasts into myofibro-blasts.Because of the nanoscale topology that regulates the mechanical transduction of cells,nanofibers or nanoparticles are commonly used to modulate fibroblast differentiation.However,the strength of nanofibers is insufficient,and the physi-ological toxicity of nanoparticles still remains to be verified.In this study,self-induced crystallization was used to construct nano-protrusions on the random and aligned polycaprolactone microfibers to regulate the behavior of fibroblasts.The results revealed that the mechanical properties of microfibers with a nanoscale topology were improved.Immunofluorescence staining manifested that nano-protrusions impeded the activation of integrins and vinculins,thereby inhibiting the nuclear transfer of Yes-associated protein,resulting in a decrease in the expression ofα-smooth muscle actin.Nanoscale topology of microfibers hampered the activation of the Rho/ROCK signalling pathway.In general,we used a simple process to con-struct a fibrous scaffold with a micro-nano multilevel structure.This structure can hinder the transformation of fibroblasts into myofibroblasts on both random and aligned fibers,which is expected to prevent fibrosis.
基金support from the National Natural Science Foundation of China(No.62061011)the Guangxi Zhuang Autonomous Region(Nos.2018GXNSFAA281253 and 2019GXNSFGA245006)the High-Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes.
文摘AB_(2)O_(4)-type spinels with low relative permittivity(ε_(τ))and high quality factor(Q×f)are crucial to high-speed signal propagation systems.In this work,Zn^(2+)/Ge^(4+) co-doping to substitute Ga in ZnGa_(2)O_(4) was designed to lower the sintering temperature and adjust the thermal stability of resonance frequency simultaneously.Zn_(1+2)Ga_(2-2x)Ge_(x)O_(4)(0.1≤x≤0.5)ceramics were synthesised by the conventional solid state method.Zn^(2+)/Ge^(4+) co-substitution induced minimal variation in the macroscopical spinel structure,which effectively lowered the sintering temperature from 1385 to 1250℃.All compositions crystallized in a normal spinel structure and exhibited dense microstructures and excellent microwave dielectric properties.The compositional dependent quality factor was related to the microstructural variation,being confirmed by Raman features.A composition with x=0.3 shows the best dielectric properties with ε_(τ) ≈10.09,Q×f≈112,700 THz,and ε_(τ) ≈-75.6 ppm/℃.The negative τf value was further adjusted to be near-zero through the formation of composite ceramics with TiO_(2).
基金the National Natural Science Foundation of China(grant no.22108218)“Young Talent Support Plan”of Xi'an Jiaotong University(71211201010723)+6 种基金This work was financially supported by the China Postdoctoral Science Foundation(Grant No.2021M693813)Guangxi Science and Technology Base and Talents Special Project(Grant No.AD21159007)the Natural Science Foundation of Guangxi(Grant No.2020GXNSFBA297029)the Foundation of Key Laboratory of New Processing Technology for Nonferrous Metal&Materials,Ministry of Education/Guangxi Key Laboratory of Optical and Electronic Materials and Devices,Guilin University of Technology(Contract No.20AA-13)the Foundation of Guilin University of Tech-nology(GLUTQDJJ2020003)High Level Innovation Team and Outstanding Scholar Program of Guangxi Institutes.We acknowledge DESY(Hamburg,Germany),a member of the Helmholtz Association HGF,and Paul Scherrer Institut(Villigen PSI,Switzerland)for the provision of experimental facilitiescontributes to the research performed at CELEST(Center for Electro-chemical Energy Storage Ulm-Karlsruhe)and was supported by the German Research Foundation(DFG)under Project ID 390874152(POLiS Cluster of Excellence).
文摘Layered alkali-containing 3d transition-metal oxides are of the utmost importance in the use of electrode materials for advanced energy storage applications such as Li-,Na-,or K-ion batteries.A significant challenge in the field of materials chemistry is understanding the dynamics of the chemical reactions between alkali-free precursors and alkali species during the synthesis of these compounds.In this study,in situ high-resolution synchrotron-based X-ray diffraction was applied to reveal the Li/Na/K-ion insertion-induced structural transformation mechanism during high-temperature solid-state reaction.The in situ diffraction results demonstrate that the chemical reaction pathway strongly depends on the alkali-free precursor type,which is a structural matrix enabling phase transi-tions.Quantitative phase analysis identifies for the first time the decomposition of lithium sources as the most critical factor for the formation of metastable intermediates or impurities during the entire process of Li-rich layered Li[Li_(0.2)Ni_(0.2)Mn_(0.6)]O_(2) formation.Since the alkali ions have different ionic radii,Na/K ions tend to be located on prismatic sites in the defective layered structure(Na_(2/3-x)[Ni_(0.25)Mn_(0.75)]O_(2) or K_(2/3-x)[Ni_(0.25)Mn_(0.75)]O_(2))during calcination,whereas the Li ions prefer to be localized on the tetrahedral and/or octahedral sites,forming O-type structures.
基金Fundamental Research Funds of Shaanxi Key Laboratory of Artificially-Structured Functional Materials and Devices(No.AFMD-KFJJ-21210)the financial support from the National Natural Science Foundation of China(No.62061011)Guangxi Key Laboratory Fund of Embedded Technology and Intelligent System(No.2020-1-6).
文摘High-entropy effect is a novel design strategy to optimize properties and explore novel materials.In this work,(La_(1/5)Nd_(1/5)Sm_(1/5)Ho_(1/5)Y_(1/5))NbO_(4)(5RNO)high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature(S.T.)range of 1210–1290℃via a solid-phase reaction route,and medium-entropy(La_(1/3)Nd_(1/3)Sm_(1/3))NbO_(4) and(La_(1/4)Nd_(1/4)Sm_(1/4)Ho_(1/4))NbO_(4)(3RNO and 4RNO)ceramics were compared.The effects of the entropy(S)on crystal structure,phase transition,and dielectric performance were evaluated.The entropy increase yields a significant increase in a phase transition temperature(from monoclinic fergusonite to tetragonal scheelite structure).Optimal microwave dielectric properties were achieved in the high-entropy ceramics(5RNO)at the sintering temperature of 1270℃for 4 h with a relative density of 98.2%and microwave dielectric properties of dielectric permittirity(ε_(r))=19.48,quality factor(Q×f)=47,770 GHz,and resonant frequency temperature coefficient(τ_(f))=–13.50 ppm/℃.This work opens an avenue for the exploration of novel microwave dielectric material and property optimization via entropy engineering.
基金supported by the National Natural Science Foundation of China(51402196,51973170)the Innovation Project of Guangxi Graduate Education(YCSW2020047)+3 种基金the Guangxi Natural Science Foundation(2017GXNSFFA198015)the open Foundation of Guangxi Key Laboratory of Optical and Electronic Materials and Devices(20KF-6)the Natural Science Foundation of Shaanxi Province(Grant No.2019JCW-17,2020JCW-15)the Development and Planning Guide Foundation of Xidian University(Grant No.21103200005).
文摘Ferroelectric thin/thick films with large electrocaloric(EC)effect are critical for solid state cooling technologies.Here,large positive EC effects with two EC peaks in a broad temperature range(~100 K)were obtained in 0.95Pb_(0.92)La_(0.08)(Zr_(0.70)Ti_(0.30))_(0.98)O_(3)-0.05BiFeO_(3)(BFO-La-codoped PZT)epitaxial thin films deposited on the(100),(110)and(111)oriented SrTiO_(3)(STO)substrates by a sol-gel method.The thin film deposited on the(111)oriented STO substrate exhibited a stronger EC effect(~20.6 K at 1956 kV/cm)near room temperature.However,the thin films deposited on the(100)and(110)oriented STO substrates exhibited a stronger EC effect(~18.8 K at 1852 kV/cm and~20.8 K at 1230 kV/cm,respectively)around the peak of the dielectric permittivity(T_(m),~375 K).Particularly,as the direction of the applied electric field was switched(E<0),the DT of the(100)-oriented thin films around T_(m) was enhanced significantly from 18.8 K to 38.1 K.The self-induced-poling during the preparing process maybe plays a key role on the magic phenomenon.It can be concluded that the BFO-La-codoped PZT epitaxial thin films are promising candidates for application in the next solid-state cooling devices.
基金This work was financially supported by the Natural Science Foundation of China(Grant Nos.11564010,11264010,21061004 and 50962004)by the Natural Science Foundation of Guangxi(Grant No.GA139008).
文摘CaCu_(3)Ti_(4-x)Y_(x)O_(12)(0≤x≤0.12)ceramics were fabricated with conventional solid-state reaction method.Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM),respectively.The impedance and modulus tests both suggested the existence of two different relaxation behavior,which were attributed to bulk and grain boundary response.In addition,the conductivity and dielectric permittivity showed a step-like behavior under 405 K.Meanwhile,frequency independence of dc conduction became dominant when above 405 K.In CCTO ceramic,rare earth element Y^(3+)ions as an acceptor were used to substitute Ti sites,decreasing the concentration of oxygen vacancy around grainelectrode and grain boundary.The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.
