Layered sodium trititanate(Na_(2)Ti_(3)O_(7),NTO)is a promising anode material for sodium-ion batteries(NIBs)for large-scale energy storage applications because of its relatively low charge potential and low cost.Howe...Layered sodium trititanate(Na_(2)Ti_(3)O_(7),NTO)is a promising anode material for sodium-ion batteries(NIBs)for large-scale energy storage applications because of its relatively low charge potential and low cost.However,NTO suffers from unsatisfactory structural stability against cycling and poor electron conductivity.Herein,an isovalent doping strategy using Sn^(4+)to partially replace Ti^(4+)is demonstrated for improving the cycling stability and rate capability of NTO.The isovalent doping of Sn^(4+)does not alter the valence state of Ti^(4+),thus maintaining the lattice integrality and structural stability.Moreover,the Sn^(4+)dopant creates more Na^(+)-preferable travel channels and expands the interlayer spacing,thus increasing Na^(+)diffusivity.As a result,a Sn^(4+)-doped Na_(2)Ti_(3)O_7(NSTO)electrode exhibits a reversible Na^(+)storage specific capacity of 176 mA h g^(-1)at 0.1C and an ultra-long cycling life with 80.2%capacity retention after5000 cycles at 1C,far outperforming the undoped and aliovalent-doping NTO electrodes reported in the literature.In addition,the NSTO electrode delivers a rate capability of 102 mA h g^(-1)at 5C,higher than that of the NTO electrode(62 mA h g^(-1)).In situ X-ray diffraction characterization results reveal that Na^(+)storage in NSTO undergoes a partial solid-solution reaction mechanism,which is completely different from the two-phase transition mechanism of NTO.Density functional theory calculation results demonstrate that Sn^(4+)doping strengthens the Ti-O bond,contributing to structural stability.This work provides a robust approach to significantly improving the electrochemical performance of NTO-based anode materials for developing long-life NIBs.展开更多
A tetragonal polymorph of lanthanum orthoniobate can be stabilized to room temperature by the substitution of Nb with an isovalent element.LaNb_(1−x)As_(x)O_(4)(0<x≤0.3),where As is an element stabilizing the tetr...A tetragonal polymorph of lanthanum orthoniobate can be stabilized to room temperature by the substitution of Nb with an isovalent element.LaNb_(1−x)As_(x)O_(4)(0<x≤0.3),where As is an element stabilizing the tetragonal structure,were successfully synthesized using a combined co-precipitation and solid-state reaction method.展开更多
The development of Eu-based chalcogenides with exceptional nonlinear optical(NLO)performance in the infrared(IR)region has garnered increasing attention.However,the design and synthesis of such compounds with non-cent...The development of Eu-based chalcogenides with exceptional nonlinear optical(NLO)performance in the infrared(IR)region has garnered increasing attention.However,the design and synthesis of such compounds with non-centrosymmetric(NCS)structures remain a significant challenge.In this study,we report the successful synthesis of a novel quaternary Eu-based chalcogenide,β-EuZnGeS_(4),achieved through an isovalent cation substitution strategy starting from the ternary parent compound Eu_(2)GeS_(4).This innovative approach induces a structural transformation from centrosymmetric to non-centrosymmetric,thereby enhancing the NLO properties.β-EuZnGeS_(4)crystallizes in the orthorhombic Fdd2 space group,with a unique two-dimensional[ZnGeS_(4)]^(2−) layer structure that accommodates Eu^(2+)cations.Notably,β-EuZnGeS_(4) exhibits a well-balanced set of optical properties,including a remarkable phasematching second-harmonic generation(SHG)effect,with its maximum SHG value being twice that of AgGaS_(2) with a 2050 nm laser.Additionally,it exhibits a high laser-induced damage threshold,surpassing AgGaS_(2) by a factor of 13.1,along with a broad transparency window extending from 0.39 to 23.7μm.Theoretical calculations further reveal that these outstanding optical properties stem from the synergistic effects of the highly distorted tetrahedral[ZnS_(4)]and[GeS_(4)]motifs within the crystal lattice.This work not only expands the materials database for rare-earth metal chalcogenides but also provides a novel strategy for designing NCS structures with tailored optical properties for a wide range of applications.展开更多
BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric(TE)material at nearly room temperature.To improve its low thermoelectric figure of merit(zT),in this work,Sb and Te isovalent c...BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric(TE)material at nearly room temperature.To improve its low thermoelectric figure of merit(zT),in this work,Sb and Te isovalent co-alloying was performed and significantly optimized its TE property with weakly anisotropic characteristic.After substituting Sb on Bi sites,the carrier concentration is suppressed by introduction of Sbsingle bond Se site defects,which contributes to the increased absolute value of Seebeck coefficient(|S|).Further co-alloying Te on Se of the optimized composition Bi_(0.7)Sb_(0.3)Se,the carrier concentration increased without affecting the|S|due to the enhanced effective mass,which leads to a highest power factor of 12.8μW/(cm·K^(2))at 423 K.As a result,a maximum zT of∼0.54 is achieved for Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3) along the pressing direction and the average zT(zTave)(from 300 K to 623 K)are drastically improved from 0.24 for pristine BiSe sample to 0.45.Moreover,an energy conversion efficiency∼4.0%is achieved for a single leg TE device of Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3)when applied the temperature difference of 339 K,indicating the potential TE application.展开更多
An experimental study was carried out on the sorption of tetravalent ions Zr4+ and Hf4+ onto hydrous ferric oxide (HFO) and their fractionation behavior during colloid/solution interaction. The sorption of the isovale...An experimental study was carried out on the sorption of tetravalent ions Zr4+ and Hf4+ onto hydrous ferric oxide (HFO) and their fractionation behavior during colloid/solution interaction. The sorption of the isovalent ions Zr4+ and Hf4+ onto HFO is nonlinear, and they are fractionated during the sorption and co-precipitation processes: Zr4+ is more affinitive for HFO than Hf4+. At pH<6, the Zr/Hf ratios in solid phase decrease sharply with increasing pH values, but keep unchanged at pH>6. In both cases, the sorption/desorption or particle/water reaction can significantly fractionate Zr/Hf in the surface environment of the Earth.展开更多
Lanthanum cerate(La_(2)Ce_(2)O_(7),LC)is a promising thermal barrier coating(TBC)candidate with superior thermophysical properties over yttria-stabilized zirconia(YSZ),but its practical application is hindered by low-...Lanthanum cerate(La_(2)Ce_(2)O_(7),LC)is a promising thermal barrier coating(TBC)candidate with superior thermophysical properties over yttria-stabilized zirconia(YSZ),but its practical application is hindered by low-temperature thermal expansion coefficient(TEC)contraction.Previous studies primarily focused on regulating the oxygen vacancy concentration while neglecting the influences of vacancy distribution.Herein,we employ Sm^(3+)isovalent substitution for La^(3+)to maintain a constant vacancy concentration and isolate the vacancy distribution effects.The optimal composition(La_(0.8)Sm_(0.2))_(2)Ce_(2)O_(7)significantly suppresses low-temperature contraction,reducing the linear shrinkage rate by~88.5%and increasing the TEC by~12.56%(to 12.37×10^(-6)K^(-1))compared with LC(10.99×10^(-6)K^(-1)).Combining density functional theory(DFT)calculations and HR-TEM/AC-STEM characterization,we directly reveal Sm^(3+)-induced oxygen vacancy clustering in LC-based ceramics.The underlying mechanism involves(i)randomly distributed free vacancies inducing contraction via vacancy-phonon coupling and local symmetry breaking;(ii)Sm^(3+)substitution introducing dislocations whose stress fields,together with Sm^(3+)’s higher ionic potential,drive vacancy clustering;(iii)clustering reducing mobile vacancies and restoring lattice order,thereby suppressing contraction.This work confirms that LC's low-temperature contraction is coregulated by vacancy concentration and distribution,complementing existing concentration-modulation strategies.展开更多
基金supported by the Natural Science Foundation of Shandong Province(ZR2022QB025 and ZR2021QF070)the Start-up Foundation of Qingdao University(DC2000005025)。
文摘Layered sodium trititanate(Na_(2)Ti_(3)O_(7),NTO)is a promising anode material for sodium-ion batteries(NIBs)for large-scale energy storage applications because of its relatively low charge potential and low cost.However,NTO suffers from unsatisfactory structural stability against cycling and poor electron conductivity.Herein,an isovalent doping strategy using Sn^(4+)to partially replace Ti^(4+)is demonstrated for improving the cycling stability and rate capability of NTO.The isovalent doping of Sn^(4+)does not alter the valence state of Ti^(4+),thus maintaining the lattice integrality and structural stability.Moreover,the Sn^(4+)dopant creates more Na^(+)-preferable travel channels and expands the interlayer spacing,thus increasing Na^(+)diffusivity.As a result,a Sn^(4+)-doped Na_(2)Ti_(3)O_7(NSTO)electrode exhibits a reversible Na^(+)storage specific capacity of 176 mA h g^(-1)at 0.1C and an ultra-long cycling life with 80.2%capacity retention after5000 cycles at 1C,far outperforming the undoped and aliovalent-doping NTO electrodes reported in the literature.In addition,the NSTO electrode delivers a rate capability of 102 mA h g^(-1)at 5C,higher than that of the NTO electrode(62 mA h g^(-1)).In situ X-ray diffraction characterization results reveal that Na^(+)storage in NSTO undergoes a partial solid-solution reaction mechanism,which is completely different from the two-phase transition mechanism of NTO.Density functional theory calculation results demonstrate that Sn^(4+)doping strengthens the Ti-O bond,contributing to structural stability.This work provides a robust approach to significantly improving the electrochemical performance of NTO-based anode materials for developing long-life NIBs.
基金financially supported by the National Science Centre,Poland,Grant No.2015/17/N/ST5/02813.
文摘A tetragonal polymorph of lanthanum orthoniobate can be stabilized to room temperature by the substitution of Nb with an isovalent element.LaNb_(1−x)As_(x)O_(4)(0<x≤0.3),where As is an element stabilizing the tetragonal structure,were successfully synthesized using a combined co-precipitation and solid-state reaction method.
基金supported by the National Natural Science Foundation of China(22175175)Natural Science Foundation of Fujian Province(2022L3092 and 2023H0041)+1 种基金Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2021ZR118)the Youth Innovation Promotion Association CAS(2022303).
文摘The development of Eu-based chalcogenides with exceptional nonlinear optical(NLO)performance in the infrared(IR)region has garnered increasing attention.However,the design and synthesis of such compounds with non-centrosymmetric(NCS)structures remain a significant challenge.In this study,we report the successful synthesis of a novel quaternary Eu-based chalcogenide,β-EuZnGeS_(4),achieved through an isovalent cation substitution strategy starting from the ternary parent compound Eu_(2)GeS_(4).This innovative approach induces a structural transformation from centrosymmetric to non-centrosymmetric,thereby enhancing the NLO properties.β-EuZnGeS_(4)crystallizes in the orthorhombic Fdd2 space group,with a unique two-dimensional[ZnGeS_(4)]^(2−) layer structure that accommodates Eu^(2+)cations.Notably,β-EuZnGeS_(4) exhibits a well-balanced set of optical properties,including a remarkable phasematching second-harmonic generation(SHG)effect,with its maximum SHG value being twice that of AgGaS_(2) with a 2050 nm laser.Additionally,it exhibits a high laser-induced damage threshold,surpassing AgGaS_(2) by a factor of 13.1,along with a broad transparency window extending from 0.39 to 23.7μm.Theoretical calculations further reveal that these outstanding optical properties stem from the synergistic effects of the highly distorted tetrahedral[ZnS_(4)]and[GeS_(4)]motifs within the crystal lattice.This work not only expands the materials database for rare-earth metal chalcogenides but also provides a novel strategy for designing NCS structures with tailored optical properties for a wide range of applications.
基金This work was supported by the National Natural Science Foundation of China(No.52372210 and No.52072248)Natural Science Foundation of Guangdong Province of China(No.2023A1515010122 and No.2021A1515012128)Technology plan project of Shenzhen(No.20220810154601001).
文摘BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric(TE)material at nearly room temperature.To improve its low thermoelectric figure of merit(zT),in this work,Sb and Te isovalent co-alloying was performed and significantly optimized its TE property with weakly anisotropic characteristic.After substituting Sb on Bi sites,the carrier concentration is suppressed by introduction of Sbsingle bond Se site defects,which contributes to the increased absolute value of Seebeck coefficient(|S|).Further co-alloying Te on Se of the optimized composition Bi_(0.7)Sb_(0.3)Se,the carrier concentration increased without affecting the|S|due to the enhanced effective mass,which leads to a highest power factor of 12.8μW/(cm·K^(2))at 423 K.As a result,a maximum zT of∼0.54 is achieved for Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3) along the pressing direction and the average zT(zTave)(from 300 K to 623 K)are drastically improved from 0.24 for pristine BiSe sample to 0.45.Moreover,an energy conversion efficiency∼4.0%is achieved for a single leg TE device of Bi_(0.7)Sb_(0.3)Se_(0.7)Te_(0.3)when applied the temperature difference of 339 K,indicating the potential TE application.
文摘An experimental study was carried out on the sorption of tetravalent ions Zr4+ and Hf4+ onto hydrous ferric oxide (HFO) and their fractionation behavior during colloid/solution interaction. The sorption of the isovalent ions Zr4+ and Hf4+ onto HFO is nonlinear, and they are fractionated during the sorption and co-precipitation processes: Zr4+ is more affinitive for HFO than Hf4+. At pH<6, the Zr/Hf ratios in solid phase decrease sharply with increasing pH values, but keep unchanged at pH>6. In both cases, the sorption/desorption or particle/water reaction can significantly fractionate Zr/Hf in the surface environment of the Earth.
基金financially supported by the National Natural Science Foundation of China(No.52262006)Natural Science Foundation of Jiangxi Province(No.20232BAB204018)+1 种基金Doctoral Start-up Fund Project of Jiangxi Science and Technology Normal University(No.2020BSQD011)Student Innovative Project of Jiangxi Science and Technology Normal University(No.YC2024-X16).
文摘Lanthanum cerate(La_(2)Ce_(2)O_(7),LC)is a promising thermal barrier coating(TBC)candidate with superior thermophysical properties over yttria-stabilized zirconia(YSZ),but its practical application is hindered by low-temperature thermal expansion coefficient(TEC)contraction.Previous studies primarily focused on regulating the oxygen vacancy concentration while neglecting the influences of vacancy distribution.Herein,we employ Sm^(3+)isovalent substitution for La^(3+)to maintain a constant vacancy concentration and isolate the vacancy distribution effects.The optimal composition(La_(0.8)Sm_(0.2))_(2)Ce_(2)O_(7)significantly suppresses low-temperature contraction,reducing the linear shrinkage rate by~88.5%and increasing the TEC by~12.56%(to 12.37×10^(-6)K^(-1))compared with LC(10.99×10^(-6)K^(-1)).Combining density functional theory(DFT)calculations and HR-TEM/AC-STEM characterization,we directly reveal Sm^(3+)-induced oxygen vacancy clustering in LC-based ceramics.The underlying mechanism involves(i)randomly distributed free vacancies inducing contraction via vacancy-phonon coupling and local symmetry breaking;(ii)Sm^(3+)substitution introducing dislocations whose stress fields,together with Sm^(3+)’s higher ionic potential,drive vacancy clustering;(iii)clustering reducing mobile vacancies and restoring lattice order,thereby suppressing contraction.This work confirms that LC's low-temperature contraction is coregulated by vacancy concentration and distribution,complementing existing concentration-modulation strategies.
