Yttrium tantalate(YTaO_(4))is the next generation of higher service temperature thermal barrier coatings(TBCs)materials due to its smaller volume effect in phase change,lower thermal conductivity and unique ferroelast...Yttrium tantalate(YTaO_(4))is the next generation of higher service temperature thermal barrier coatings(TBCs)materials due to its smaller volume effect in phase change,lower thermal conductivity and unique ferroelastic domain structure.However,the low fracture toughness limits its application.We first characterized the diffraction patterns of variants,and two variants(M_(1)and M_(2))observed in transmission electron microscopy(TEM)results were determined from four possible variants by mechanical derivation.The role of Zr^(4+)doping in ferroelastic toughening was explained in detail.With the increase of Zr^(4+)doping concentration,the monoclinic angle β and the domain rotation angleαdecrease,respectively.The spontaneous strain component and the principal strain in the main space also have a similar decreasing trend.The decrease of the ferroelastic domain inversion energy barrier is beneficial to the improvement of fracture toughness.Combining the results of Vickers indentation,we found that Zr^(4+)could be enriched at the domain boundary to inhibit the generation of cracks.An appropriate amount of Zr^(4+)is conducive to the improvement of fracture toughness,and the excessive Zr^(4+)will reduce the fracture toughness due to the generation of by-product t-ZrO_(2).So,the optimal composition is Y_(0.44)Ta_(0.44)Zr_(0.12)O_(2) and the best fracture toughness(2.9–3.8MPa m^(1/2))is equivalent to the commercial 8YSZ.This result will promote the application of a new generation of TBCs.展开更多
The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal the...The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal theories of high-T<sub>c</sub> superconductors, thereby applying the finding that the optimum hole concentration of σ<sub>o</sub> = 0.229 can be linked with the universal fractal constant δ<sub>1</sub> = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ<sub>1</sub>, exemplified through the energy gap relation k<sub>B</sub>T<sub>c</sub> ≈ 5Δ<sub>0</sub>/δ<sub>1</sub>, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T<sub>c</sub> superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.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
Multifunctional switchable materials are attracting tremendous interest because of their great application potential in signal processing,information encryption,and smart devices.Here,we reported an organic-inorganic ...Multifunctional switchable materials are attracting tremendous interest because of their great application potential in signal processing,information encryption,and smart devices.Here,we reported an organic-inorganic hybrid thermochromic ferroelastic crystal,[TMIm][CuCl_(4)](TMIm=1,1,3,3-tetramethylimidazolidinium),which undergoes two reversible phase transitions at 333 K and 419 K,respectively.Intriguingly,these three phases experience a remarkable ferroelastic-paraelastic-ferroelastic(2/m-mmm-2/m)transition,which remains relatively unexplored in ferroelastics.Moreover,the ferroelastic domains can be simultaneously switched under temperature and stress stimuli.Meanwhile,[TMIm][CuCl_(4)]exhibits thermochromic phenomenon,endowing it with extra spectral encryption possibilities during information processing.Combined with dielectric switching behavior,[TMIm][Cu Cl_(4)]are promising for practical applications in memory devices,next-generation sensors,and encryption technology.展开更多
Thermal barrier coating(TBC)materials can improve energy conversion efficiency and reduce fossil fuel use.Herein,novel rare earth tantalates RETaO_(4),as promising candidates for TBCs,were reassembled into multi-compo...Thermal barrier coating(TBC)materials can improve energy conversion efficiency and reduce fossil fuel use.Herein,novel rare earth tantalates RETaO_(4),as promising candidates for TBCs,were reassembled into multi-component solid solutions with a monoclinic structure to further depress thermal conductivity via an entropy strategy.The formation mechanisms of oxygen vacancy defects,dislocations,and ferroelastic domains associated with the thermal conductivity are demonstrated by aberration-corrected scanning transmission electron microscopy.Compared to single-RE RETaO_(4)and 8YSZ,the intrinsic thermal conductivity of(5RE1/5)TaO4 was decreased by 35%–47%and 57%–69%at 1200℃,respectively,which is likely attributed to multi-scale phonon scattering from Umklapp phonon–phonon,point defects,domain structures,and dislocations.r¯3+RE/r5+Ta and low-temperature thermal conductivity are negatively correlated,as are the ratio of elastic modulus to thermal conductivity(E/κ)and high-temperature thermal conductivity.Meanwhile,the high defects’concentration and lattice distortion in high-entropy ceramics enhance the scattering of transverse-wave phonons and reduce the transverse-wave sound velocity,leading to a decrease in the thermal conductivity and Young’s modulus.In addition,5HEC-1 has ultra-low thermal conductivity,moderate thermal expansion coefficients,and high hardness among three five-component high-entropy samples.Thus,5HEC-1 with superior thermal barrier and mechanical properties can be used as promising thermal insulating materials.展开更多
基金the National Natural Science Foundation of China(Nos.11890684 and 52102142)the Foundation for Innovative Research Groups of Hunan Province(No.2020JJ1005)。
文摘Yttrium tantalate(YTaO_(4))is the next generation of higher service temperature thermal barrier coatings(TBCs)materials due to its smaller volume effect in phase change,lower thermal conductivity and unique ferroelastic domain structure.However,the low fracture toughness limits its application.We first characterized the diffraction patterns of variants,and two variants(M_(1)and M_(2))observed in transmission electron microscopy(TEM)results were determined from four possible variants by mechanical derivation.The role of Zr^(4+)doping in ferroelastic toughening was explained in detail.With the increase of Zr^(4+)doping concentration,the monoclinic angle β and the domain rotation angleαdecrease,respectively.The spontaneous strain component and the principal strain in the main space also have a similar decreasing trend.The decrease of the ferroelastic domain inversion energy barrier is beneficial to the improvement of fracture toughness.Combining the results of Vickers indentation,we found that Zr^(4+)could be enriched at the domain boundary to inhibit the generation of cracks.An appropriate amount of Zr^(4+)is conducive to the improvement of fracture toughness,and the excessive Zr^(4+)will reduce the fracture toughness due to the generation of by-product t-ZrO_(2).So,the optimal composition is Y_(0.44)Ta_(0.44)Zr_(0.12)O_(2) and the best fracture toughness(2.9–3.8MPa m^(1/2))is equivalent to the commercial 8YSZ.This result will promote the application of a new generation of TBCs.
文摘The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal theories of high-T<sub>c</sub> superconductors, thereby applying the finding that the optimum hole concentration of σ<sub>o</sub> = 0.229 can be linked with the universal fractal constant δ<sub>1</sub> = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ<sub>1</sub>, exemplified through the energy gap relation k<sub>B</sub>T<sub>c</sub> ≈ 5Δ<sub>0</sub>/δ<sub>1</sub>, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T<sub>c</sub> superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.
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supported by the National Natural Science Foundation of China(Nos.21975114,11904151 and 22105094)。
文摘Multifunctional switchable materials are attracting tremendous interest because of their great application potential in signal processing,information encryption,and smart devices.Here,we reported an organic-inorganic hybrid thermochromic ferroelastic crystal,[TMIm][CuCl_(4)](TMIm=1,1,3,3-tetramethylimidazolidinium),which undergoes two reversible phase transitions at 333 K and 419 K,respectively.Intriguingly,these three phases experience a remarkable ferroelastic-paraelastic-ferroelastic(2/m-mmm-2/m)transition,which remains relatively unexplored in ferroelastics.Moreover,the ferroelastic domains can be simultaneously switched under temperature and stress stimuli.Meanwhile,[TMIm][CuCl_(4)]exhibits thermochromic phenomenon,endowing it with extra spectral encryption possibilities during information processing.Combined with dielectric switching behavior,[TMIm][Cu Cl_(4)]are promising for practical applications in memory devices,next-generation sensors,and encryption technology.
基金supported by the National Key R&D Program of China(No.2022YFB3708600)the Materials Genome Engineering of Rare and Precious Metal of Yunnan Province(No.202102AB080019-1)+1 种基金Yunnan Fundamental Research Projects(Nos.202101AW070011,202101BE070001-015)Kunming University of Science and Technology Analysis and Testing Fund(No.2022P20211130017).
文摘Thermal barrier coating(TBC)materials can improve energy conversion efficiency and reduce fossil fuel use.Herein,novel rare earth tantalates RETaO_(4),as promising candidates for TBCs,were reassembled into multi-component solid solutions with a monoclinic structure to further depress thermal conductivity via an entropy strategy.The formation mechanisms of oxygen vacancy defects,dislocations,and ferroelastic domains associated with the thermal conductivity are demonstrated by aberration-corrected scanning transmission electron microscopy.Compared to single-RE RETaO_(4)and 8YSZ,the intrinsic thermal conductivity of(5RE1/5)TaO4 was decreased by 35%–47%and 57%–69%at 1200℃,respectively,which is likely attributed to multi-scale phonon scattering from Umklapp phonon–phonon,point defects,domain structures,and dislocations.r¯3+RE/r5+Ta and low-temperature thermal conductivity are negatively correlated,as are the ratio of elastic modulus to thermal conductivity(E/κ)and high-temperature thermal conductivity.Meanwhile,the high defects’concentration and lattice distortion in high-entropy ceramics enhance the scattering of transverse-wave phonons and reduce the transverse-wave sound velocity,leading to a decrease in the thermal conductivity and Young’s modulus.In addition,5HEC-1 has ultra-low thermal conductivity,moderate thermal expansion coefficients,and high hardness among three five-component high-entropy samples.Thus,5HEC-1 with superior thermal barrier and mechanical properties can be used as promising thermal insulating materials.