Two novel phosphors LiBa_(4(1-x))Eu_(4x)Ta_(3)O_(12)(H-LBTO:xEu^(3+)) and Li_(0.25)Ba_(1-x)Eu_(x)Ta_(0.75)O_(3)(C-LBTO:xEu^(3+))were prepared successfully by a molten salt method.The transformation between these two s...Two novel phosphors LiBa_(4(1-x))Eu_(4x)Ta_(3)O_(12)(H-LBTO:xEu^(3+)) and Li_(0.25)Ba_(1-x)Eu_(x)Ta_(0.75)O_(3)(C-LBTO:xEu^(3+))were prepared successfully by a molten salt method.The transformation between these two structures was realized by changing the sintering temperature or changing the Eu^(3+) ions concentration,which was also demonstrated by the X-ray diffraction(XRD),scanning electron microscopy(SEM),diffuse reflectance spectra(DRS),and photoluminescence excitation(PLE) analyses,Both the sintering temperature and the Eu^(3+)ions doping concentration have significant impact on the formation of the crystal phase.All these phosphors sintered at 1023 K exhibit two major luminescence lines at 594 and 614 nm under nearUV light of 395 nm excitation,corresponding to Eu^(3+)ions typical transitions of ^(5)D_(0)→^(7)F_(1) and ^(5)D_(0)→^(7)F_(2).The optimum concentration of Eu^(3+) ions is 9 mol% for C-LBTO:xEu^(3+) samples and the quenching interaction type is the nearest-neighbor ion interaction.The thermal stability of the C-LBTO:0.09Eu^(3+)sample was investigated in detail and the device application further suggests that C-LBTO:0.09Eu^(3+) can be used as a red phosphor for near-UV excited w-LEDs in lighting.展开更多
This work aims at mapping the compositions of zinc tantalate for optimum photocatalytic performance in degradation of organic pollutants. Three zinc tantalates, low-temperature form ZnTa2O6 （LT-ZnTa2O6）, high-temper...This work aims at mapping the compositions of zinc tantalate for optimum photocatalytic performance in degradation of organic pollutants. Three zinc tantalates, low-temperature form ZnTa2O6 （LT-ZnTa2O6）, high-temperature form ZnTa2O6 （HT-ZnTa2O6）, and Zn3Ta2O8 were prepared by solid state method. Photocatalytic activities of these zinc tantalates were tested for the degradation of methyl orange under UV irradiation and compared with Sr2Ta2O7, an efficient catalyst previously reported. It is found that the photocatalytic activity of these tantalates follows such a sequence： LT-ZnTa2O6 〉 Sr2Ta2O7 〉 HT-ZnTa2O6 〉 Zn3Ta2O8, in which LT-ZnTa2O6 shows an optimum activity at least twice higher than Sr2Ta2O7. This photocatalytic performance was revealed to primarily originate from the formation of ·OH radicals as indicated by photo- luminescence measurements. The synergistic effects of chemical compositions, crystal structure, and band structure on photocatalytic performances were discussed.展开更多
Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties.However,its high photorefraction and slow electro-optic response relaxation i...Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties.However,its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors.Recently,lithium tantalate,another piezoelectric and nonlinear material,has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction,faster electro-optic response relaxation,higher optical damage threshold,wider transparency window,and lower birefringence compared with lithium niobate.Here,we developed an ultralow-loss lithium tantalate integrated photonic platform,including waveguides,grating couplers,and microring cavities.The measured highest optical Q factor of the microring cavities is beyond 10^(7),corresponding to the lowest waveguide propagation loss of~1.88 dB∕m.The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities.This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices,such as periodically poled waveguides,acousto-optic modulators,and electro-optic modulators.展开更多
Chip-based soliton frequency microcombs combine compact size,broad bandwidth,and high coherence,presenting a promising solution for integrated optical telecommunications,precision sensing,and spectroscopy.Recent progr...Chip-based soliton frequency microcombs combine compact size,broad bandwidth,and high coherence,presenting a promising solution for integrated optical telecommunications,precision sensing,and spectroscopy.Recent progress in ferroelectric thin films,particularly thin-film lithium niobate(LiNbO_(3))and thin-film lithium tantalate(LiTaO_(3)),has significantly advanced electro-optic(EO)modulation and soliton microcombs generation,leveraging their strong third-order nonlinearity and high Pockels coefficients.However,achieving soliton frequency combs in X-cut ferroelectric materials remains challenging due to the competing effects of thermo-optic and photorefractive phenomena.These issues hinder the simultaneous realization of soliton generation and high-speed EO modulation.Here,following the thermal-regulated carrier behavior and auxiliary-laser-assisted approach,we propose a convenient mechanism to suppress both photorefractive and thermal dragging effects at once,and implement a facile method for soliton formation and its longterm stabilization in integrated X-cut LiTaO_(3) microresonators for the first time,to the best of our knowledge.The resulting mode-locked states exhibit robust stability against perturbations,enabling new pathways for fully integrated photonic circuits that combine Kerr nonlinearity with high-speed EO functionality.展开更多
Rare-earth tantalates and niobates(REjTaO7 and REjNbO7)have been considered as promising candidate thermal barrier coating(TBC)materials in next generation gas-turbine engines due to their ultra-low thermal conductivi...Rare-earth tantalates and niobates(REjTaO7 and REjNbO7)have been considered as promising candidate thermal barrier coating(TBC)materials in next generation gas-turbine engines due to their ultra-low thermal conductivity and better thermal stability than yttria-stabilized zirconia(YSZ).However,the low Vickers hardness and toughness are the main shortcomings of RE;TaO-and REjNbOr that limit their applications as TBC materials.To increase the hardness,high entropy(Yu3Ybu3Er/3)sTaOr,(Y13YbnErns)NbO,and(Sm1/6Eu1/6Y 1/6Yb1/6Lu1/6Er1/6)3(Nb1/2Ta1/2)O7 are designed and synthesized in this study.These high entropy ceramics exhibit high Vickers hardness(10.912.0 GPa),close thermal expansion coefficients to that of single-principal-component RE3TaO,and RE;NbO,(7.9×10^-6-10.8×10-6 C-1 at room temperature),good phase stability,and good chemical compatibility with thermally grown Al2O3,which make them promising for applications as candidate TBC materials.展开更多
Electro-optic(EO)crystals are important material for all-solid-state laser technology,which can be used to fabricate various laser modulators,such as EO switches,laser deflectors,and optical waveguide.The improvements...Electro-optic(EO)crystals are important material for all-solid-state laser technology,which can be used to fabricate various laser modulators,such as EO switches,laser deflectors,and optical waveguide.The improvements in new high-efficiency EO crystal materials have held great significance to the development of laser technology.Potassium tantalate niobate(KTN)is a popular multifunctional crystal because of its remarkable and excellent quadratic EO effect.KTN EO modulation technology offers numerous advantages,such as high efficiency,good stability,a quick response time,and inertia-free characteristics.In this paper,we summarize the research progress of KTN series crystals systemically,including the theoretical exploration on quadratic EO effect,solid-melt crystal growth technique,comprehensive physical characterization,new physical effect and mechanisms exploration,new EO devices development and design.The EO modulation technique based on the Kerr effect of KTN series crystal offers obvious advantages in reducing the drive voltage and device size,which could better meet the developmental needs of future lasers with a wide wavelength,miniaturization,and integration.This may provide theoretical guidance and an experimental basis for the design and development of new EO crystal devices and promote the development of laser technology.展开更多
Monoclinic yttrium tantalate (M'-YTaO4,M'-YTO),and two different kinds of yttrium niobium-tantalate (M'-YTao.85Nbo.15O4 (M'-YTNO) and Eu3+ doped M'-YTao.85Nbo.15O4 (M'-YTNO∶Eu3+)) were produce...Monoclinic yttrium tantalate (M'-YTaO4,M'-YTO),and two different kinds of yttrium niobium-tantalate (M'-YTao.85Nbo.15O4 (M'-YTNO) and Eu3+ doped M'-YTao.85Nbo.15O4 (M'-YTNO∶Eu3+)) were produced by sol-gel method and grown on single crystalline Si (100) substrate by spin coating approach.Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD),atomic force microscopy (AFM),scanning electron microscopy (SEM),and thermogravimetry and differential thermal analysis (TG-DTA).Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu3+ were presented.The photoluminescence spectra of the films exhibited strong blue (380-400 nm) and red (614 nm) emissions upon ultraviolet excitation.Emission intensities were strongly dependent on the host lattice composition and film morphology.1.5％ Eu3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm.To the best of our knowledge,this is the first attempt in the production of M'-YTO,M'-YTNO,and M'-YTNO∶Eu3+ films on single crystalline Si (100) substrate via sol-gel spin coating.展开更多
The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)an...The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)and Sr_(x)Ba_(1-x)Nb_(2)O_(6)(SBN).Several experimental methods have been used for visualization of the micro-and nanodomain patterns.The static domain images have been obtained by optical microscopy and piezoresponse force microscopy.The Raman confocal microscopy allowed us to obtain the domain images in the bulk.The equilibrium slow switching with effective screening resulted in growth of polygon-shaped microdomains:hexagons in LN,triangles in LT and squares in SBN,which corresponds to crystal symmetry.Switching in nonequilibrium conditions(noneffective screening of depolarization field)brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes:(1)formation of nanodomain ensembles,(2)discrete switching,(3)incomplete merging and(4)spontaneous backswitching.展开更多
Thermal/environmental barrier coatings(T/EBCs)are used to protect hot-section superalloys and/or ceramic matrix composite components from hot corrosion and oxidation;however,the majority of T/EBCs exhibit extremely hi...Thermal/environmental barrier coatings(T/EBCs)are used to protect hot-section superalloys and/or ceramic matrix composite components from hot corrosion and oxidation;however,the majority of T/EBCs exhibit extremely high thermal and ionic conductivities.Here,we obtain a novel rare-earth tantalate with excellent oxygen and thermal insulation via a high-entropy strategy.The high-entropy component(8RE_(1/8))TaO_(4)(RE=rare earth),which is designed by large size disorder and mass disorder,has been reassembled into a stabilized monoclinic structure.(8RE_(1/8))TaO_(4)had 30.0%–31.1%and 59.2%–67.5%lower intrinsic thermal conductivity than single-RE RETaO_(4)and 8(Y_(2)O_(3)–ZrO_(2))8YSZ at 1200℃,respectively,and exhibited lower intrinsic thermal conductivity across the entire temperature range of 100–1200℃.This is the result of strong scattering by the phonon–phonon,grain boundary,domain boundary,dislocation,and vacancy defects.The ionic conductivity of(8RE_(1/8))TaO_(4)is 3712–29,667 times lower than that of 8YSZ at 900℃,benefiting from the strong Ta–O bonding strength,low concentration of mobile oxygen vacancies and severe lattice distortions that impede carrier transport.Moreover,(8RE_(1/8))TaO_(4)had superior high-temperature stability and excellent mechanical properties.Analysis of above results demonstrates that(8RE_(1/8))TaO_(4)is a promising candidate for T/EBCs.展开更多
In contrast to research on active sites in nanomaterials,lithium tantalate single crystals,known for their exceptional optical properties and long-range ordered lattice structure,present a promising avenue for in-dept...In contrast to research on active sites in nanomaterials,lithium tantalate single crystals,known for their exceptional optical properties and long-range ordered lattice structure,present a promising avenue for in-depth exploration of photocatalytic reaction systems with fewer constraints imposed by surface chemistry.Typically,the isotropy of a specific facet provides a perfect support for studying heteroatom doping.Herein,this work delves into the intrinsic catalytic sites for photocatalytic nitrogen fixation in iron-doped lithium tantalate single crystals.The presence of iron not only modifies the electronic structure of lithium tantalate,improving its light absorption capacity,but also functions as an active site for the nitrogen adsorption and activation.The photocatalytic ammonia production rate of the iron-doped lithium tantalate in pure water is maximum 26.95μg cm^(−2)h^(−1),which is three times higher than that of undoped lithium tantalate.The combination of first-principles simulations with in situ characterizations confirms that iron doping promotes the rate-determining step and changes the pathway of hydrogenation to associative alternating.This study provides a new perspective on in-depth investigation of intrinsic catalytic active sites in photocatalysis and other catalytic processes.展开更多
Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research...Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research used chemical co-precipitation within an automated experimental device to synthesize RETaO_(4)(RE=Nd,Sm,Gd,Ho,Er)powders.The device automatically monitored and controlled the solutions'pH,improving the chemical co-precipitation efficiency.The crystal structure and microstructure of the RETaO_(4)powders can be controlled by changing the annealing temperature,and the materials undergo an m'-m phase transition.The m'-RETaO_(4)powders exhibit nano-size grains,while m-RETaO_(4)powders evince micron-size grains,altered by the annealing temperatures.A simultaneous thermal analysis es-timates the reversive ferroelastic tetragonal-monoclinic phase transition temperatures.Overall,this research focuses on the synthesis,crystal structures,microstructures,and phase transition of the fabricated RETaO_(4)powders.展开更多
Thermal and mechanical properties of yttrium tantalate(YTaO_(4)),a top coat ceramic of thermal barrier coatings(TBCs)for aeroengines,are enhanced by synthesizing Y_(1-x)Ta_(1-x)M_(2x)O_(4)(M=Ti,Zr,Hf;x=0.06,0.12,0.18,...Thermal and mechanical properties of yttrium tantalate(YTaO_(4)),a top coat ceramic of thermal barrier coatings(TBCs)for aeroengines,are enhanced by synthesizing Y_(1-x)Ta_(1-x)M_(2x)O_(4)(M=Ti,Zr,Hf;x=0.06,0.12,0.18,0.24)medium-entropy ceramics(MECs)using a two-step sintering method.In addition,the thermal conductivity,thermal expansion coefficients(TECs),and fracture toughness of MECs were investigated.An X-ray diffraction study revealed that the Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs were monoclinic,and the Ti,Zr,and Hf doping elements replaced Y and Ta.The variations in atomic weights and ionic radii led to disturbed atomic arrangements and severe lattice distortions,resulting in improving the phonon scattering and reduced thermal conductivity,with Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)exhibiting the lowest thermal conductivity of 1.23 W·m^(-1)·K^(-1)at 900℃.The introduction of MO_(2) increased the configurational entropy and weakened the ionic bonding energy,obtaining high TECs(10.4×10^(-6)K^(-1)at 1400℃).The reduction in the monoclinic angle β lowered the ferroelastic domain inversion energy barrier.Moreover,microcracks and crack extension toughening endowed Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)with the highest fracture toughness of(4.1±0.5)MPa·m~(1/2).The simultaneous improvement of the thermal and mechanical properties of the MO_(2)(M=Ti,Zr,Hf)co-doped YTaO_(4) MECs can be extended to other materials.展开更多
The controllable synthesis of tantalate K1.9Na0.1Ta2O6·2H2O has been successfully achieved by a two-step technique,namely,the molten salt and hydrothermal methods,at a low temperature. By simply varying the KOH c...The controllable synthesis of tantalate K1.9Na0.1Ta2O6·2H2O has been successfully achieved by a two-step technique,namely,the molten salt and hydrothermal methods,at a low temperature. By simply varying the KOH concentration in the hydrothermal process,K1.9Na0.1Ta2O6·2H2O particles with spherical,cuboctahedral,and durian-like morphologies were synthesized. The photocatalytic activity of the obtained samples for the degradation of rhodamine B was studied under ultraviolet light,which indicates that the photocatalytic properties of the samples are highly dependent on their morphologies. The K1.9Na0.1Ta2O6·2H2O nanospheres,with rough surfaces and the highest specific surface area,exhibit the best performance. The present work provides a unique approach for the controlled synthesis of tantalate photocatalysts,which are difficult to achieve through other synthetic approaches.展开更多
The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)G...The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)Gd_(0.1)Dy_(0.1)Ho_(0.1)Er_(0.1)Tm_(0.1)Yb_(0.1)Lu_(0.1))TaO_(4)((10RE_(0.1))TaO_(4))is synthesized successfully.The lat-tice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates.Notably,compared with single rare-earth tantalates,the thermal conductivity of(10RE_(0.1))TaO_(4) is reduced by 16%-45%at 100℃ and 22%-45%at 800℃,and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200℃.The phonon thermal conductivity(1.0-2.2 W m^(-1) K^(-1),100-1200℃)of(10RE_(0.1))TaO_(4) is lower than that of the currently reported high-entropy four-,five-and six-component rare-earth tantalates.This is the result of scattering by the ferroelastic domain,lattice distortion associated with size and mass disorder,and point defects,which target low-,mid-and high-frequency phonons.Furthermore,(10RE_(0.1))TaO_(4),as an improved candidate for thermal barrier coatings materials(TBCs),has a higher thermal expansion coefficient(10.5×10^(-6)K^(-1) at 1400℃),lower Young’s modulus(123 GPa)and better high-temperature phase stability than that of single rare-earth tantalates.展开更多
A novel red-emitting phosphor tantalate Ca_(2)YTaO_(6):Eu^(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_(2)YTaO_(6):Eu^(3+)phosphors show a ...A novel red-emitting phosphor tantalate Ca_(2)YTaO_(6):Eu^(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_(2)YTaO_(6):Eu^(3+)phosphors show a sharp emission peak at 612 nm under near-ultraviolet(n-UV) at 395 nm because of the ^(5)D0→^(7)F_(2) transition of Eu^(3+).The optimal Eu^(3+)doping concentration in Ca_(2)YTaO_(6) is 40 mol% and the critical energy-transfer distance of Eu^(3+)ions was calculated to be 0.9 nm.The emission spectra of Ca_(2)YTaO_(6):Eu_(3+)from 300 to 480 K were investigated.The thermal-quenching temperature(T_(0.5)) of Ca_(2)YTaO_(6):Eu^(3+)is above 480 K.The color purity of Ca_(2)YTaO_(6):40 mol%Eu^(3+)is as high as 99.8%.The luminescence lifetime of Ca_(2)YTaO_(6):40 mol%Eu^(3+)was also discussed.The high color purity and high thermal stability of Eu^(3+)-doped Ca_(2)YTaO_(6) phosphors contribute to its application value in white lightemitting diodes(w-LEDs).展开更多
As candidate thermal/environmental barrier coatings(T/EBCs),the structure characteristics and comprehensive properties of monoclinic-prime(m')RETaO4(RE=Yb,Lu,Sc)with excellent Al2O3/SiO2 chemical compatibility are...As candidate thermal/environmental barrier coatings(T/EBCs),the structure characteristics and comprehensive properties of monoclinic-prime(m')RETaO4(RE=Yb,Lu,Sc)with excellent Al2O3/SiO2 chemical compatibility are studied.Excellent thermal insulation protection will be provided by m'RETaO4 due to their low thermal conductivity(~1.6 Wm^-1 K^-1,900℃)and prominent thermal radiation resistance,which is much better than those of YSZ(~2.5 Wm^-1 K^-1,1000℃)and La-12 Zr2O7(~2.0 Wm^-1 K,900℃).The thermal expansion coefficients(TECs)are 3.0–8.0×10^-6 K^-1(200-1200℃),which is suitable for T/EBCs applications.Furthermore,absence of phase transition and extraordinary chemical compatibility with Al2O3/SiO2 up to 1500℃indicate the potential application prospect.The documented governing mechanisms of m'RETaO4 properties will enable researchers to promote their application in the future investigation.展开更多
A systematic investigation concerned with Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20,respectively)ceramics was fabricated by a solid-state reaction method and characterized by X-ray diffraction(XRD),Raman spectroscop...A systematic investigation concerned with Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20,respectively)ceramics was fabricated by a solid-state reaction method and characterized by X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM)and thermal analysis.XRD spectra display that all of the samples are excellently consistent with the standard XRD spectrum of monoclinic YTaO4(PDF No.24-1415;space group:I2(5)).The Raman peaks of the samples doped with Mg2+just widen slightly compared with those of pure YTaO4,which are in agreement with the results of XRD.The thermal conductivity of dense 7 wt%–8 wt%yttria-stabilized zirconia(7–8 YSZ)ceramic is about 2.5 W·m-1·K-1at 900°C,while the Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20)ceramics possess lower thermal conductivity in the range of 1.45–1.57 W·m-1·K-1at 900°C,which declines by35%compared with that of 7–8 YSZ.The lower thermal conductivities of Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16and 0.20)ceramics are originated from the enhanced phonon scattering caused by oxygen vacancy and Mg2+ions defect complex.However,the thermal expansion coefficients are about 9.0910-6–9.5910-6K-1along with the different amounts of Mg2+doping at 1200°C.Compared to the pure sample,the thermal expansion coefficient decreases slightly when the Mg2+doping amount is over 20%.The systematic investigations on the phase,microstructure,elastic and thermal properties of Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20)ceramics will provide guidance for its application at high temperature,especially as thermal barrier coatings.展开更多
A series of Eu 3+ doped of Mtype of yttrium orthotantalate Y 1-x Eu x TaO 4( x =0-0.30) was sythesized. The influence of activator concentration on luminescence properties was studied in detail. The strong evidence fr...A series of Eu 3+ doped of Mtype of yttrium orthotantalate Y 1-x Eu x TaO 4( x =0-0.30) was sythesized. The influence of activator concentration on luminescence properties was studied in detail. The strong evidence from excitation spectra, emission spectra and diffusive reflection spectra of this system shows that there is energy transfer from TaO 3- 4 to Eu 3+ via the charge transfer and spectral overlap.展开更多
Pressure-and temperature-dependent luminescence properties of ^(3)F_(3/2)→^(4)I9/2 transition of Nd^(3+):GdTaO_(4) were studied for potential applications in optical sensing.Two isolated emission lines corresponding ...Pressure-and temperature-dependent luminescence properties of ^(3)F_(3/2)→^(4)I9/2 transition of Nd^(3+):GdTaO_(4) were studied for potential applications in optical sensing.Two isolated emission lines corresponding to^(3)F_(3/2)(R2,1)→^(4)I_(9/2)(Z5)transitions,located at 920 and 927 nm under ambient condition,are very sensitive to pressure with coefficients of-15.6 and-14.5 cm^(-1)/GPa determined in a pressure range up to about 9 GPa.The luminescence intensity ratio between the two emission lines exhibits a large dependence with temperature in a range from 80 to 620 K,the corresponding temperature sensitivity at room temperature is similar to that of Nd^(3+):YAG.These advantages,together with the other observed features of high stable position relationship under pressure and low thermal shifts for the two emission lines indicate that Nd^(3+):GdTaO_(4) is a promising candidate to be used as pressure and temperature sensors in the near-infrared spectral range.展开更多
A novel layered perovskite tantalate phosphor Sr_(3)LaTa_(3)O_(12):Sm^(3+)(SLTO:Sm^(3+)) with orange-red emission was obtained for the first time via the solid-phase synthetic method. The phase purity, surface morphol...A novel layered perovskite tantalate phosphor Sr_(3)LaTa_(3)O_(12):Sm^(3+)(SLTO:Sm^(3+)) with orange-red emission was obtained for the first time via the solid-phase synthetic method. The phase purity, surface morphology,element distribution and luminescent properties of the SLTO:xSm^(3+)(x= 0.01 mol%-0.30 mol%) phosphors were investigated. Under 408 nm excitation, the optimum doped SLTO:0.10Sm^(3+) phosphor emits orangered light at 598 nm with the highest emission peak(4G_(5/2)→6H_(7/2)). The critical energy transfer distance is 1.687 nm. The prepared SLTO:0.10Sm^(3+)phosphor has excellent thermal stability with temperature quenching temperature(T_(0.5)> 500 K) and high activation energy(E_(a)= 0.25 e V). Through calculation, the chromaticity coordinates of all samples are concentrated in the orange-red area, and the color purity reaches 99%. The fabricated white light-emitting diode(w-LED) has a good correlated color temperature(5132 K), a high R_(a)(89), and the CIE chromaticity coordinates(0.340, 0.327). Consequently, the superiority of orange-red-emitting tantalate SLTO:Sm^(3+) phosphors for w-LEDs is demonstrated.展开更多
基金supported by the Foundation of Fujian Provincial Department (2021J011149)。
文摘Two novel phosphors LiBa_(4(1-x))Eu_(4x)Ta_(3)O_(12)(H-LBTO:xEu^(3+)) and Li_(0.25)Ba_(1-x)Eu_(x)Ta_(0.75)O_(3)(C-LBTO:xEu^(3+))were prepared successfully by a molten salt method.The transformation between these two structures was realized by changing the sintering temperature or changing the Eu^(3+) ions concentration,which was also demonstrated by the X-ray diffraction(XRD),scanning electron microscopy(SEM),diffuse reflectance spectra(DRS),and photoluminescence excitation(PLE) analyses,Both the sintering temperature and the Eu^(3+)ions doping concentration have significant impact on the formation of the crystal phase.All these phosphors sintered at 1023 K exhibit two major luminescence lines at 594 and 614 nm under nearUV light of 395 nm excitation,corresponding to Eu^(3+)ions typical transitions of ^(5)D_(0)→^(7)F_(1) and ^(5)D_(0)→^(7)F_(2).The optimum concentration of Eu^(3+) ions is 9 mol% for C-LBTO:xEu^(3+) samples and the quenching interaction type is the nearest-neighbor ion interaction.The thermal stability of the C-LBTO:0.09Eu^(3+)sample was investigated in detail and the device application further suggests that C-LBTO:0.09Eu^(3+) can be used as a red phosphor for near-UV excited w-LEDs in lighting.
文摘This work aims at mapping the compositions of zinc tantalate for optimum photocatalytic performance in degradation of organic pollutants. Three zinc tantalates, low-temperature form ZnTa2O6 （LT-ZnTa2O6）, high-temperature form ZnTa2O6 （HT-ZnTa2O6）, and Zn3Ta2O8 were prepared by solid state method. Photocatalytic activities of these zinc tantalates were tested for the degradation of methyl orange under UV irradiation and compared with Sr2Ta2O7, an efficient catalyst previously reported. It is found that the photocatalytic activity of these tantalates follows such a sequence： LT-ZnTa2O6 〉 Sr2Ta2O7 〉 HT-ZnTa2O6 〉 Zn3Ta2O8, in which LT-ZnTa2O6 shows an optimum activity at least twice higher than Sr2Ta2O7. This photocatalytic performance was revealed to primarily originate from the formation of ·OH radicals as indicated by photo- luminescence measurements. The synergistic effects of chemical compositions, crystal structure, and band structure on photocatalytic performances were discussed.
基金Research Grants Council of Hong Kong(C4050-21E,RFS2324-4S03,14203623)The Chinese University of Hong Kong(Group Research Scheme)。
文摘Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties.However,its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors.Recently,lithium tantalate,another piezoelectric and nonlinear material,has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction,faster electro-optic response relaxation,higher optical damage threshold,wider transparency window,and lower birefringence compared with lithium niobate.Here,we developed an ultralow-loss lithium tantalate integrated photonic platform,including waveguides,grating couplers,and microring cavities.The measured highest optical Q factor of the microring cavities is beyond 10^(7),corresponding to the lowest waveguide propagation loss of~1.88 dB∕m.The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities.This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices,such as periodically poled waveguides,acousto-optic modulators,and electro-optic modulators.
基金National Key Research and Development Program of China(2022YFA1404601)National Natural Science Foundation of China(62293520,62293521,12074400,62205363,12104442,12404446,12293052)+4 种基金Shanghai Science and Technology Innovation Action Plan Program(20JC1416200,22JC1403300)CAS Project for Young Scientists in Basic Research(YSBR-69)Natural Science Foundation of Anhui Province(2408085QA010)China Postdoctoral Science Foundation(2024M753078)Postdoctoral Fellowship Program of CPSF(GZC20232560)。
文摘Chip-based soliton frequency microcombs combine compact size,broad bandwidth,and high coherence,presenting a promising solution for integrated optical telecommunications,precision sensing,and spectroscopy.Recent progress in ferroelectric thin films,particularly thin-film lithium niobate(LiNbO_(3))and thin-film lithium tantalate(LiTaO_(3)),has significantly advanced electro-optic(EO)modulation and soliton microcombs generation,leveraging their strong third-order nonlinearity and high Pockels coefficients.However,achieving soliton frequency combs in X-cut ferroelectric materials remains challenging due to the competing effects of thermo-optic and photorefractive phenomena.These issues hinder the simultaneous realization of soliton generation and high-speed EO modulation.Here,following the thermal-regulated carrier behavior and auxiliary-laser-assisted approach,we propose a convenient mechanism to suppress both photorefractive and thermal dragging effects at once,and implement a facile method for soliton formation and its longterm stabilization in integrated X-cut LiTaO_(3) microresonators for the first time,to the best of our knowledge.The resulting mode-locked states exhibit robust stability against perturbations,enabling new pathways for fully integrated photonic circuits that combine Kerr nonlinearity with high-speed EO functionality.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.51672064 and 51972089).
文摘Rare-earth tantalates and niobates(REjTaO7 and REjNbO7)have been considered as promising candidate thermal barrier coating(TBC)materials in next generation gas-turbine engines due to their ultra-low thermal conductivity and better thermal stability than yttria-stabilized zirconia(YSZ).However,the low Vickers hardness and toughness are the main shortcomings of RE;TaO-and REjNbOr that limit their applications as TBC materials.To increase the hardness,high entropy(Yu3Ybu3Er/3)sTaOr,(Y13YbnErns)NbO,and(Sm1/6Eu1/6Y 1/6Yb1/6Lu1/6Er1/6)3(Nb1/2Ta1/2)O7 are designed and synthesized in this study.These high entropy ceramics exhibit high Vickers hardness(10.912.0 GPa),close thermal expansion coefficients to that of single-principal-component RE3TaO,and RE;NbO,(7.9×10^-6-10.8×10-6 C-1 at room temperature),good phase stability,and good chemical compatibility with thermally grown Al2O3,which make them promising for applications as candidate TBC materials.
基金supported by the National Natural Science Foundation of China(52072189,and 51972179)Natural Science Foundation of Shandong Province(ZR2020KE019 and ZR2020QE041)+3 种基金Science and Technology Program for Young Innovation Team in Colleges and Universities of Shandong Province,China(2019KJA003)Studio for the Leader of Scientific Research in Jinan(2019GXRC059)Major Innovation Project for Integrating Science,Education&Industry of Qilu University of Technology(Shandong Academy of Sciences)(2022PYI015 and 2022JBZ01-07)Innovation Capability Improvement Project for Small and Mediumsized Technology-based Enterprise of Shandong Province,China(2022TSGC1357).
文摘Electro-optic(EO)crystals are important material for all-solid-state laser technology,which can be used to fabricate various laser modulators,such as EO switches,laser deflectors,and optical waveguide.The improvements in new high-efficiency EO crystal materials have held great significance to the development of laser technology.Potassium tantalate niobate(KTN)is a popular multifunctional crystal because of its remarkable and excellent quadratic EO effect.KTN EO modulation technology offers numerous advantages,such as high efficiency,good stability,a quick response time,and inertia-free characteristics.In this paper,we summarize the research progress of KTN series crystals systemically,including the theoretical exploration on quadratic EO effect,solid-melt crystal growth technique,comprehensive physical characterization,new physical effect and mechanisms exploration,new EO devices development and design.The EO modulation technique based on the Kerr effect of KTN series crystal offers obvious advantages in reducing the drive voltage and device size,which could better meet the developmental needs of future lasers with a wide wavelength,miniaturization,and integration.This may provide theoretical guidance and an experimental basis for the design and development of new EO crystal devices and promote the development of laser technology.
文摘Monoclinic yttrium tantalate (M'-YTaO4,M'-YTO),and two different kinds of yttrium niobium-tantalate (M'-YTao.85Nbo.15O4 (M'-YTNO) and Eu3+ doped M'-YTao.85Nbo.15O4 (M'-YTNO∶Eu3+)) were produced by sol-gel method and grown on single crystalline Si (100) substrate by spin coating approach.Structural properties and thermal behaviours of the films were characterized by means of X-ray diffraction (XRD),atomic force microscopy (AFM),scanning electron microscopy (SEM),and thermogravimetry and differential thermal analysis (TG-DTA).Systematic Steady-state photoluminescence and lifetime measurements in a series of yttrium niobium-tantalate with varying amounts of Eu3+ were presented.The photoluminescence spectra of the films exhibited strong blue (380-400 nm) and red (614 nm) emissions upon ultraviolet excitation.Emission intensities were strongly dependent on the host lattice composition and film morphology.1.5％ Eu3+ doped films exhibited the brightest luminescence and long lifetime extending to 1.22 ms when excited at 254 nm.To the best of our knowledge,this is the first attempt in the production of M'-YTO,M'-YTNO,and M'-YTNO∶Eu3+ films on single crystalline Si (100) substrate via sol-gel spin coating.
文摘The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)and Sr_(x)Ba_(1-x)Nb_(2)O_(6)(SBN).Several experimental methods have been used for visualization of the micro-and nanodomain patterns.The static domain images have been obtained by optical microscopy and piezoresponse force microscopy.The Raman confocal microscopy allowed us to obtain the domain images in the bulk.The equilibrium slow switching with effective screening resulted in growth of polygon-shaped microdomains:hexagons in LN,triangles in LT and squares in SBN,which corresponds to crystal symmetry.Switching in nonequilibrium conditions(noneffective screening of depolarization field)brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes:(1)formation of nanodomain ensembles,(2)discrete switching,(3)incomplete merging and(4)spontaneous backswitching.
基金supported by the National Natural Science Foundation of China(No.52402077)the Open Project of Shaanxi Laboratory(No.2021SXSYS-01-05)+1 种基金the Open Project of Yunnan Precious Metals Laboratory(No.YPML-2023050240)the Yunnan Fundamental Research Projects(Nos.202201BE070001-008,202201AT070192,and 202101BE070001-011).
文摘Thermal/environmental barrier coatings(T/EBCs)are used to protect hot-section superalloys and/or ceramic matrix composite components from hot corrosion and oxidation;however,the majority of T/EBCs exhibit extremely high thermal and ionic conductivities.Here,we obtain a novel rare-earth tantalate with excellent oxygen and thermal insulation via a high-entropy strategy.The high-entropy component(8RE_(1/8))TaO_(4)(RE=rare earth),which is designed by large size disorder and mass disorder,has been reassembled into a stabilized monoclinic structure.(8RE_(1/8))TaO_(4)had 30.0%–31.1%and 59.2%–67.5%lower intrinsic thermal conductivity than single-RE RETaO_(4)and 8(Y_(2)O_(3)–ZrO_(2))8YSZ at 1200℃,respectively,and exhibited lower intrinsic thermal conductivity across the entire temperature range of 100–1200℃.This is the result of strong scattering by the phonon–phonon,grain boundary,domain boundary,dislocation,and vacancy defects.The ionic conductivity of(8RE_(1/8))TaO_(4)is 3712–29,667 times lower than that of 8YSZ at 900℃,benefiting from the strong Ta–O bonding strength,low concentration of mobile oxygen vacancies and severe lattice distortions that impede carrier transport.Moreover,(8RE_(1/8))TaO_(4)had superior high-temperature stability and excellent mechanical properties.Analysis of above results demonstrates that(8RE_(1/8))TaO_(4)is a promising candidate for T/EBCs.
基金supported by Natural Science Foundation of Shandong Province(Nos.ZR2022YQ42,ZR2021JQ15,ZR2021QE011,ZR2021ZD20,2022GJJLJRC-01)Innovative Team Project of Jinan(No.2021GXRC019)the National Natural Science Foundation of China(Nos.52022037,52202366).
文摘In contrast to research on active sites in nanomaterials,lithium tantalate single crystals,known for their exceptional optical properties and long-range ordered lattice structure,present a promising avenue for in-depth exploration of photocatalytic reaction systems with fewer constraints imposed by surface chemistry.Typically,the isotropy of a specific facet provides a perfect support for studying heteroatom doping.Herein,this work delves into the intrinsic catalytic sites for photocatalytic nitrogen fixation in iron-doped lithium tantalate single crystals.The presence of iron not only modifies the electronic structure of lithium tantalate,improving its light absorption capacity,but also functions as an active site for the nitrogen adsorption and activation.The photocatalytic ammonia production rate of the iron-doped lithium tantalate in pure water is maximum 26.95μg cm^(−2)h^(−1),which is three times higher than that of undoped lithium tantalate.The combination of first-principles simulations with in situ characterizations confirms that iron doping promotes the rate-determining step and changes the pathway of hydrogenation to associative alternating.This study provides a new perspective on in-depth investigation of intrinsic catalytic active sites in photocatalysis and other catalytic processes.
基金the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province(202102AB080019-1)National Key Research and Development Program of China(2022YFB3708600)the National Natural Science Foundation of China(91960103).
文摘Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research used chemical co-precipitation within an automated experimental device to synthesize RETaO_(4)(RE=Nd,Sm,Gd,Ho,Er)powders.The device automatically monitored and controlled the solutions'pH,improving the chemical co-precipitation efficiency.The crystal structure and microstructure of the RETaO_(4)powders can be controlled by changing the annealing temperature,and the materials undergo an m'-m phase transition.The m'-RETaO_(4)powders exhibit nano-size grains,while m-RETaO_(4)powders evince micron-size grains,altered by the annealing temperatures.A simultaneous thermal analysis es-timates the reversive ferroelastic tetragonal-monoclinic phase transition temperatures.Overall,this research focuses on the synthesis,crystal structures,microstructures,and phase transition of the fabricated RETaO_(4)powders.
文摘Thermal and mechanical properties of yttrium tantalate(YTaO_(4)),a top coat ceramic of thermal barrier coatings(TBCs)for aeroengines,are enhanced by synthesizing Y_(1-x)Ta_(1-x)M_(2x)O_(4)(M=Ti,Zr,Hf;x=0.06,0.12,0.18,0.24)medium-entropy ceramics(MECs)using a two-step sintering method.In addition,the thermal conductivity,thermal expansion coefficients(TECs),and fracture toughness of MECs were investigated.An X-ray diffraction study revealed that the Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs were monoclinic,and the Ti,Zr,and Hf doping elements replaced Y and Ta.The variations in atomic weights and ionic radii led to disturbed atomic arrangements and severe lattice distortions,resulting in improving the phonon scattering and reduced thermal conductivity,with Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)exhibiting the lowest thermal conductivity of 1.23 W·m^(-1)·K^(-1)at 900℃.The introduction of MO_(2) increased the configurational entropy and weakened the ionic bonding energy,obtaining high TECs(10.4×10^(-6)K^(-1)at 1400℃).The reduction in the monoclinic angle β lowered the ferroelastic domain inversion energy barrier.Moreover,microcracks and crack extension toughening endowed Y_(1-x)Ta_(1-x)M_(2x)O_(4) MECs(x=0.24)with the highest fracture toughness of(4.1±0.5)MPa·m~(1/2).The simultaneous improvement of the thermal and mechanical properties of the MO_(2)(M=Ti,Zr,Hf)co-doped YTaO_(4) MECs can be extended to other materials.
基金supported by the National Natural Science Foundation of China(U140319321473261+3 种基金41305112)the Excellent Youth Foundation of Xinjiang Uygur Autonomous Region(2013711004)the CAS "Light of West China" Program(YB201303)the CAS/SAFEA International Partnership Program for Creative Research Teams~~
文摘The controllable synthesis of tantalate K1.9Na0.1Ta2O6·2H2O has been successfully achieved by a two-step technique,namely,the molten salt and hydrothermal methods,at a low temperature. By simply varying the KOH concentration in the hydrothermal process,K1.9Na0.1Ta2O6·2H2O particles with spherical,cuboctahedral,and durian-like morphologies were synthesized. The photocatalytic activity of the obtained samples for the degradation of rhodamine B was studied under ultraviolet light,which indicates that the photocatalytic properties of the samples are highly dependent on their morphologies. The K1.9Na0.1Ta2O6·2H2O nanospheres,with rough surfaces and the highest specific surface area,exhibit the best performance. The present work provides a unique approach for the controlled synthesis of tantalate photocatalysts,which are difficult to achieve through other synthetic approaches.
基金financially supported by the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province(Nos.202102AB080019-1 and 202002AB080001-1)the Yun-nan Fundamental Research Projects(Nos.202101AW070011 and 202101BE070001-015).
文摘The primary purpose of this work is to optimize the thermophysical properties of rare-earth tan-talate ceramics using the high-entropy effect.Here,the high-entropy rare-earth tantalate ceramic(Y_(0.1)Nd_(0.1)Sm_(0.1)Gd_(0.1)Dy_(0.1)Ho_(0.1)Er_(0.1)Tm_(0.1)Yb_(0.1)Lu_(0.1))TaO_(4)((10RE_(0.1))TaO_(4))is synthesized successfully.The lat-tice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates.Notably,compared with single rare-earth tantalates,the thermal conductivity of(10RE_(0.1))TaO_(4) is reduced by 16%-45%at 100℃ and 22%-45%at 800℃,and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200℃.The phonon thermal conductivity(1.0-2.2 W m^(-1) K^(-1),100-1200℃)of(10RE_(0.1))TaO_(4) is lower than that of the currently reported high-entropy four-,five-and six-component rare-earth tantalates.This is the result of scattering by the ferroelastic domain,lattice distortion associated with size and mass disorder,and point defects,which target low-,mid-and high-frequency phonons.Furthermore,(10RE_(0.1))TaO_(4),as an improved candidate for thermal barrier coatings materials(TBCs),has a higher thermal expansion coefficient(10.5×10^(-6)K^(-1) at 1400℃),lower Young’s modulus(123 GPa)and better high-temperature phase stability than that of single rare-earth tantalates.
基金The work was supported by Undergraduate Innovation Fund of Northwest A&F UniversityChina(201910712069)+3 种基金Hunan Provincial Key Laboratory of Xiangnan Rare-Precious Metals Compounds and Applications(2019XGJSKFJJ01)the Construction Program of the key discipline in Hunan Provincethe Projects of the Education Department of Hunan Province(No.18A465)Science and Technology Plan Project of Chenzhou City(jsyf2017014)。
文摘A novel red-emitting phosphor tantalate Ca_(2)YTaO_(6):Eu^(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_(2)YTaO_(6):Eu^(3+)phosphors show a sharp emission peak at 612 nm under near-ultraviolet(n-UV) at 395 nm because of the ^(5)D0→^(7)F_(2) transition of Eu^(3+).The optimal Eu^(3+)doping concentration in Ca_(2)YTaO_(6) is 40 mol% and the critical energy-transfer distance of Eu^(3+)ions was calculated to be 0.9 nm.The emission spectra of Ca_(2)YTaO_(6):Eu_(3+)from 300 to 480 K were investigated.The thermal-quenching temperature(T_(0.5)) of Ca_(2)YTaO_(6):Eu^(3+)is above 480 K.The color purity of Ca_(2)YTaO_(6):40 mol%Eu^(3+)is as high as 99.8%.The luminescence lifetime of Ca_(2)YTaO_(6):40 mol%Eu^(3+)was also discussed.The high color purity and high thermal stability of Eu^(3+)-doped Ca_(2)YTaO_(6) phosphors contribute to its application value in white lightemitting diodes(w-LEDs).
基金under the support of the Natural Science Foundation of China(No.51762028,No.91960103)Materials Genome Engineering of Rare and Precious Metal of Yunnan Province(No.2018ZE019)。
文摘As candidate thermal/environmental barrier coatings(T/EBCs),the structure characteristics and comprehensive properties of monoclinic-prime(m')RETaO4(RE=Yb,Lu,Sc)with excellent Al2O3/SiO2 chemical compatibility are studied.Excellent thermal insulation protection will be provided by m'RETaO4 due to their low thermal conductivity(~1.6 Wm^-1 K^-1,900℃)and prominent thermal radiation resistance,which is much better than those of YSZ(~2.5 Wm^-1 K^-1,1000℃)and La-12 Zr2O7(~2.0 Wm^-1 K,900℃).The thermal expansion coefficients(TECs)are 3.0–8.0×10^-6 K^-1(200-1200℃),which is suitable for T/EBCs applications.Furthermore,absence of phase transition and extraordinary chemical compatibility with Al2O3/SiO2 up to 1500℃indicate the potential application prospect.The documented governing mechanisms of m'RETaO4 properties will enable researchers to promote their application in the future investigation.
基金financially supported by the National Natural Science Foundation of China(No.51762028)the Key Project of Science&Technology in Yunnan Province.(No.2018ZE019)。
文摘A systematic investigation concerned with Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20,respectively)ceramics was fabricated by a solid-state reaction method and characterized by X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM)and thermal analysis.XRD spectra display that all of the samples are excellently consistent with the standard XRD spectrum of monoclinic YTaO4(PDF No.24-1415;space group:I2(5)).The Raman peaks of the samples doped with Mg2+just widen slightly compared with those of pure YTaO4,which are in agreement with the results of XRD.The thermal conductivity of dense 7 wt%–8 wt%yttria-stabilized zirconia(7–8 YSZ)ceramic is about 2.5 W·m-1·K-1at 900°C,while the Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20)ceramics possess lower thermal conductivity in the range of 1.45–1.57 W·m-1·K-1at 900°C,which declines by35%compared with that of 7–8 YSZ.The lower thermal conductivities of Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16and 0.20)ceramics are originated from the enhanced phonon scattering caused by oxygen vacancy and Mg2+ions defect complex.However,the thermal expansion coefficients are about 9.0910-6–9.5910-6K-1along with the different amounts of Mg2+doping at 1200°C.Compared to the pure sample,the thermal expansion coefficient decreases slightly when the Mg2+doping amount is over 20%.The systematic investigations on the phase,microstructure,elastic and thermal properties of Y1-xMgxTaO4-x/2(x=0,0.08,0.12,0.16 and 0.20)ceramics will provide guidance for its application at high temperature,especially as thermal barrier coatings.
文摘A series of Eu 3+ doped of Mtype of yttrium orthotantalate Y 1-x Eu x TaO 4( x =0-0.30) was sythesized. The influence of activator concentration on luminescence properties was studied in detail. The strong evidence from excitation spectra, emission spectra and diffusive reflection spectra of this system shows that there is energy transfer from TaO 3- 4 to Eu 3+ via the charge transfer and spectral overlap.
基金Project supported by the National Natural Science Foundation of China(11804047)Science and Technology Development Program of Jilin City(201831733)Development Program of Education Department of Jilin Province(JJKH20180425KJ)。
文摘Pressure-and temperature-dependent luminescence properties of ^(3)F_(3/2)→^(4)I9/2 transition of Nd^(3+):GdTaO_(4) were studied for potential applications in optical sensing.Two isolated emission lines corresponding to^(3)F_(3/2)(R2,1)→^(4)I_(9/2)(Z5)transitions,located at 920 and 927 nm under ambient condition,are very sensitive to pressure with coefficients of-15.6 and-14.5 cm^(-1)/GPa determined in a pressure range up to about 9 GPa.The luminescence intensity ratio between the two emission lines exhibits a large dependence with temperature in a range from 80 to 620 K,the corresponding temperature sensitivity at room temperature is similar to that of Nd^(3+):YAG.These advantages,together with the other observed features of high stable position relationship under pressure and low thermal shifts for the two emission lines indicate that Nd^(3+):GdTaO_(4) is a promising candidate to be used as pressure and temperature sensors in the near-infrared spectral range.
基金Project supported by the Hunan Provincial Key Laboratory of Xiangnan Rare-Precious Metals Compounds and Applications(2019XGJSKFJJ01)the Construction Program of the Key Discipline of the Education Department in Hunan Province(18A465)+1 种基金the Natural Science Foundation of Hunan Province(2023JJ31000)the Natural Science Foundation of Shaanxi Province(2022NY-224)。
文摘A novel layered perovskite tantalate phosphor Sr_(3)LaTa_(3)O_(12):Sm^(3+)(SLTO:Sm^(3+)) with orange-red emission was obtained for the first time via the solid-phase synthetic method. The phase purity, surface morphology,element distribution and luminescent properties of the SLTO:xSm^(3+)(x= 0.01 mol%-0.30 mol%) phosphors were investigated. Under 408 nm excitation, the optimum doped SLTO:0.10Sm^(3+) phosphor emits orangered light at 598 nm with the highest emission peak(4G_(5/2)→6H_(7/2)). The critical energy transfer distance is 1.687 nm. The prepared SLTO:0.10Sm^(3+)phosphor has excellent thermal stability with temperature quenching temperature(T_(0.5)> 500 K) and high activation energy(E_(a)= 0.25 e V). Through calculation, the chromaticity coordinates of all samples are concentrated in the orange-red area, and the color purity reaches 99%. The fabricated white light-emitting diode(w-LED) has a good correlated color temperature(5132 K), a high R_(a)(89), and the CIE chromaticity coordinates(0.340, 0.327). Consequently, the superiority of orange-red-emitting tantalate SLTO:Sm^(3+) phosphors for w-LEDs is demonstrated.
