采用固相烧结法制备ZrV 2-x P x O 7系列材料,研究了P替代对ZrV 2O 7介电和电导性能的影响。研究发现,ZrV 2-x P x O 7系列材料的高频介电常数随着P含量的增加而降低;材料的离子弛豫极化和晶界极化速率随P含量的增加先变大后变小,其介...采用固相烧结法制备ZrV 2-x P x O 7系列材料,研究了P替代对ZrV 2O 7介电和电导性能的影响。研究发现,ZrV 2-x P x O 7系列材料的高频介电常数随着P含量的增加而降低;材料的离子弛豫极化和晶界极化速率随P含量的增加先变大后变小,其介电弛豫时间随P含量的增加先增大再减小,其中ZrV 1.6 P 0.4 O 7具有最大的介电弛豫时间,为5.63×10-4 s。由于P和V离子半径和电负性的差异,P的加入会导致晶格畸变和散射几率变化。室温下,ZrV 2-x P x O 7系列材料的电导率对P的含量非常敏感,ZrV 1.6 P 0.4 O 7具有最大电导率,为5.83×10-5 S·cm-1。对ZrV 1.6 P 0.4 O 7进行变温特性测试发现,其活化能为0.19 eV。对ZrV 2-x P x O 7系列材料的电导率和介电的研究对拓展此类材料在电子器件方面的应用具有重要意义。展开更多
Large thermal expansion at room temperature and high phase transition temperature of ZrV2O7 limit its practical applications and are reduced by the high solubility of hetero-valence ion (Cu^2+) on the basis of an e...Large thermal expansion at room temperature and high phase transition temperature of ZrV2O7 limit its practical applications and are reduced by the high solubility of hetero-valence ion (Cu^2+) on the basis of an equal-valence substitution of P^5+ for V^5+. The temperature-dependent Raman spectra show that Zr0.9CU0.1V1.6P0.4O6.9 maintains a normal parent cubic structure till 173 K and transforms to a 3 × 3 × 3 cubic superstructure below 173K. Temperature dependent x-ray diffraction patterns of Zr0.9CU0.1V1.6P0.4O6.9 show near zero and negative thermal expansion. High solubility of lower valence Cu^2+ relates to an equal-valence substitution of smaller pH for P^5+, which extends the bond angle of V(P)-O-V in ZrV1.6P0.4O7 close to 180°. The change of microstructure is considered to be responsible for reduced phase transition temperature and thermal expansion.展开更多
Among all the known electrode materials, vanadium pentoxide(V_(2)O_(5)) has high reversible capacity. It is a very valuable material for research of the complexity, rich structure and morphology. However, it also has ...Among all the known electrode materials, vanadium pentoxide(V_(2)O_(5)) has high reversible capacity. It is a very valuable material for research of the complexity, rich structure and morphology. However, it also has some disadvantages,such as poor cycle stability, low discharge voltage, low conductivity and Li^(+) diffusion coefficient. In this regard, researchers have carried out a lot of research, such as using various methods to improve the nanostructures, introducing heterostructures,introducing point defects or cation doping in the crystal structure, etc. The electrochemical performance of V_(2)O_(5)has been significantly improved in reversible capacity, high-rate capacity and long-term cycle stability. In this paper, V_(2)O_(5)based nanostructure with different chemical composition are briefly introduced, and it covers V_(2)O_(5)nanomaterials with different morphology, including 1D nanorods, nanobelts, nanotubes, 2D leaf like nanosheets and other nanosheets, and 3D hollow structures, porous nanostructures, porous eggshell microsphere structures. The composite nanomaterials of V_(2)O_(5)and different carbonaceous supports are also introduced. Finally, the V_(2)O_(5)composite materials doped with cations are discussed. The electrochemical performance of V_(2)O_(5)based electrode can be improved effectively by obtaining appropriate nanostructure and optimized chemical composition.展开更多
Materials with the formula Yb2-xAlxMo3O12 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray po...Materials with the formula Yb2-xAlxMo3O12 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffraction, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3012 solid solutions crystallize in a single monoclinic phase for 1.7 〈 x 〈 2.0 and in a single orthorhombic phase for 0.0 〈 x 〈 0,4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhonlbic phase transition temperature of A12Mo3012 can be reduced by partial substitution of A13+ by Yb3+, and the Yb2-zAlxMo3012 (0.0 〈 x 〈 2.0) materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of A13+ for Yb3+ in Yb2Mo3012 decreases its hygroscopicity, and the linear thermal expansion coefficients after complete removal of water species are measured to be -9.1 x 10-6/K, -5.5 x 10-6/K, 5.74 x 10-6/K, and 9.5 x 10 6/K for Ybl.sAlo.2(MoO4)3, Yb1.6Alo.4(MoO4)3, Ybo.4All.6(Mo04)3, and Ybo.2Al1.8(MoO4)3, respectively.展开更多
A solid solution of (HfSc)0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm ...A solid solution of (HfSc)0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm (47) and exhibits negative thermal expansion (NTE) property with low anisotropy in thermal expansion. The coefficients of thermal expansion (CTEs) for a, b, and c axes are -1.41×10^-6 K^-1, -2.23×10^-6 K^-1, and -1.87×10^-6 K^-1, respectively. This gives rise to volume and linear CTEs of -3.10×10^-6 K^-1 and -1.03×10^-6 K^-1, respectively. Besides, it exhibits also intense photoluminescence from 360 nm to about 600 nm. The mechanism of NTE and the correlation of the PL with axial thermal expansion property are discussed.展开更多
Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grai...Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y2-x(ZnLi)xMo3O12(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn^2+ and Li+for Y^3+ in Y2Mo3O12 resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y2-x(ZnLi)xMo3O12 could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.展开更多
Low thermal expansion materials are mostly ceramics with low conductive property, which limits their applications in electronic devices. The poor conductive property of ceramic ZrV_2 O_7 could be improved by bi-substi...Low thermal expansion materials are mostly ceramics with low conductive property, which limits their applications in electronic devices. The poor conductive property of ceramic ZrV_2 O_7 could be improved by bi-substitution of Fe and Mo for Zr and V, accompanied with low thermal expansion. Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 has electrical conductivity of 8.2× 10^(-5) S/cm and 9.41× 10^(-4) S/cm at 291 K and 623 K, respectively. From 291 K to 413 K, thermal excitation leads to the increase of carrier concentration, which causes the rapid decrease of resistance. At 413–533 K, the conductivity is unchanged due to high scattering probability and a slowing increase of carrier concentration. The conductivity rapidly increases again from533 K to 623 K due to the intrinsic thermal excitation. The thermal expansion coefficient of Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 is as low as 0.72× 10^(-6 )K^(-1) at 140–700 K from the dilatometer measurement. These properties suggest that Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 has attractive application in electronic components.展开更多
Solid solutions of In2(1-x)(HfMg)xMo3O12 are synthesized by solid state reaction with the aim to reduce the phase transition temperature of In2Mo3O12 and improve its thermal expansion property.The effects of(HfMg...Solid solutions of In2(1-x)(HfMg)xMo3O12 are synthesized by solid state reaction with the aim to reduce the phase transition temperature of In2Mo3O12 and improve its thermal expansion property.The effects of(HfMg)^6+ incorporation on the phase transition and thermal expansion are investigated.It is shown that the monoclinic-to-orthorhombic phase transition temperature obviously decreases and the coefficient of thermal expansion(CTE) of the orthorhombic becomes less negative and approaches to zero with increasing the content of(HfMg)^6+.A near zero thermal expansion covering the case at room temperature(RT) is achieved for the solid solutions with x ≥ 0.85,implying potential applications of this material in many fields.展开更多
Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12(x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9) are synthesized, and the effects of Zr4+ and Mg2+ co-incorporation on the phase transition, thermal expansion, and Ra...Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12(x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9) are synthesized, and the effects of Zr4+ and Mg2+ co-incorporation on the phase transition, thermal expansion, and Raman mode are investigated. It is found that Cr2-xZr0.5xMg0.5xMo3O12 crystallize into monoclinic structures for x 〈 1.3 and orthorhombic structures for x _〉 1.5 at room temperature. The phase transition temperature from a monoclinic to an orthorhombic structure of Cr2Mo3O12 can be reduced by the partial substitution of (ZrMg)6+ for Cr3+. The overall linear thermal expansion coefficient decreases with the increase of the (ZrMg)6+ content in an orthorhombic structure sample. The co-incorporation of Zr4+ and Mg2+ in the lattice results in the occurrence of new Raman modes and the hardening of the symmetric vibrational modes, which are attributed to the MoO4 tetrahedra sharing comers with ZrO6/MgO6 octahedra and to the strengthening of Mo-O bonds due to less electronegativities of Zr4+ and Mg2+ than Cr3+, respectively.展开更多
A material with the formula ZrMgMo_(3)O_(12) having negative thermal expansion is presented and characterized.It is shown that ZrMgMo_(3)O_(12) crystallizes in an orthorhombic symmetry with space group Pnma(62)or Pna2...A material with the formula ZrMgMo_(3)O_(12) having negative thermal expansion is presented and characterized.It is shown that ZrMgMo_(3)O_(12) crystallizes in an orthorhombic symmetry with space group Pnma(62)or Pna21(33)and exhibits negative thermal expansion in a large temperature range(αl=-3.8×10^(-6) K^(-1) from 300 K to 1000 K by x-ray diffraction andαl=-3.73×10^(-6) K^(-1) from 295 K to 775 K by dilatometer).ZrMgMo_(3)O_(12) remains the orthorhombic structure without phase transition or decomposition at least from 123 K to 1200 K and is not hygroscopic.These properties make it an excellent material with negative thermal expansion for a variety of applications.展开更多
文摘采用固相烧结法制备ZrV 2-x P x O 7系列材料,研究了P替代对ZrV 2O 7介电和电导性能的影响。研究发现,ZrV 2-x P x O 7系列材料的高频介电常数随着P含量的增加而降低;材料的离子弛豫极化和晶界极化速率随P含量的增加先变大后变小,其介电弛豫时间随P含量的增加先增大再减小,其中ZrV 1.6 P 0.4 O 7具有最大的介电弛豫时间,为5.63×10-4 s。由于P和V离子半径和电负性的差异,P的加入会导致晶格畸变和散射几率变化。室温下,ZrV 2-x P x O 7系列材料的电导率对P的含量非常敏感,ZrV 1.6 P 0.4 O 7具有最大电导率,为5.83×10-5 S·cm-1。对ZrV 1.6 P 0.4 O 7进行变温特性测试发现,其活化能为0.19 eV。对ZrV 2-x P x O 7系列材料的电导率和介电的研究对拓展此类材料在电子器件方面的应用具有重要意义。
基金Supported by the National Natural Science Foundation of China under Grant Nos 10974183 and 11104252, the Research Fund for the Doctoral Program of Higher Education of China under Grant No 20114101110003, the Fund for Science and Technology Innovation Team of Zhengzhou Province under Grant No l12PCXTD337, and the Postdoctoral Research Sponsorship in Henan Province under Grant No 2011002.
文摘Large thermal expansion at room temperature and high phase transition temperature of ZrV2O7 limit its practical applications and are reduced by the high solubility of hetero-valence ion (Cu^2+) on the basis of an equal-valence substitution of P^5+ for V^5+. The temperature-dependent Raman spectra show that Zr0.9CU0.1V1.6P0.4O6.9 maintains a normal parent cubic structure till 173 K and transforms to a 3 × 3 × 3 cubic superstructure below 173K. Temperature dependent x-ray diffraction patterns of Zr0.9CU0.1V1.6P0.4O6.9 show near zero and negative thermal expansion. High solubility of lower valence Cu^2+ relates to an equal-valence substitution of smaller pH for P^5+, which extends the bond angle of V(P)-O-V in ZrV1.6P0.4O7 close to 180°. The change of microstructure is considered to be responsible for reduced phase transition temperature and thermal expansion.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51702097 and U1804125)the Key Scientific and Technological Research Projects of Henan Province, China (Grant No. 202102210222)。
文摘Among all the known electrode materials, vanadium pentoxide(V_(2)O_(5)) has high reversible capacity. It is a very valuable material for research of the complexity, rich structure and morphology. However, it also has some disadvantages,such as poor cycle stability, low discharge voltage, low conductivity and Li^(+) diffusion coefficient. In this regard, researchers have carried out a lot of research, such as using various methods to improve the nanostructures, introducing heterostructures,introducing point defects or cation doping in the crystal structure, etc. The electrochemical performance of V_(2)O_(5)has been significantly improved in reversible capacity, high-rate capacity and long-term cycle stability. In this paper, V_(2)O_(5)based nanostructure with different chemical composition are briefly introduced, and it covers V_(2)O_(5)nanomaterials with different morphology, including 1D nanorods, nanobelts, nanotubes, 2D leaf like nanosheets and other nanosheets, and 3D hollow structures, porous nanostructures, porous eggshell microsphere structures. The composite nanomaterials of V_(2)O_(5)and different carbonaceous supports are also introduced. Finally, the V_(2)O_(5)composite materials doped with cations are discussed. The electrochemical performance of V_(2)O_(5)based electrode can be improved effectively by obtaining appropriate nanostructure and optimized chemical composition.
基金supported by the National Natural Science Foundation of China (Grant No. 10974183)
文摘Materials with the formula Yb2-xAlxMo3O12 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.9, 1.0, 1.1, 1.3, 1.5, and 1.8) were synthesized and their structures, phase transitions, and hygroscopicity investigated using X-ray powder diffraction, Raman spectroscopy, and thermal analysis. It is shown that Yb2-xAlxMo3012 solid solutions crystallize in a single monoclinic phase for 1.7 〈 x 〈 2.0 and in a single orthorhombic phase for 0.0 〈 x 〈 0,4, and exhibit the characteristics of both monoclinic and orthorhombic structures outside these compositional ranges. The monoclinic to orthorhonlbic phase transition temperature of A12Mo3012 can be reduced by partial substitution of A13+ by Yb3+, and the Yb2-zAlxMo3012 (0.0 〈 x 〈 2.0) materials are hydrated at room temperature and contain two kinds of water species. One of these interacts strongly with and hinders the motions of the polyhedra, while the other does not. The partial substitution of A13+ for Yb3+ in Yb2Mo3012 decreases its hygroscopicity, and the linear thermal expansion coefficients after complete removal of water species are measured to be -9.1 x 10-6/K, -5.5 x 10-6/K, 5.74 x 10-6/K, and 9.5 x 10 6/K for Ybl.sAlo.2(MoO4)3, Yb1.6Alo.4(MoO4)3, Ybo.4All.6(Mo04)3, and Ybo.2Al1.8(MoO4)3, respectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574276,51302249,and 11405028)the Fundamental Research Fund for the Central Universities,China
文摘A solid solution of (HfSc)0.83W2.25P0.83O12-δ is synthesized by the high-temperature, solid-state reaction and fast-quenching method. It is shown that it possesses an orthorhombic structure with space group Pmmm (47) and exhibits negative thermal expansion (NTE) property with low anisotropy in thermal expansion. The coefficients of thermal expansion (CTEs) for a, b, and c axes are -1.41×10^-6 K^-1, -2.23×10^-6 K^-1, and -1.87×10^-6 K^-1, respectively. This gives rise to volume and linear CTEs of -3.10×10^-6 K^-1 and -1.03×10^-6 K^-1, respectively. Besides, it exhibits also intense photoluminescence from 360 nm to about 600 nm. The mechanism of NTE and the correlation of the PL with axial thermal expansion property are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60976016,61350012,and 11574276)the Key Scientific Research Projects of Henan Province,China(Grant No.15B140004)+2 种基金Henan Science and Technology Development Project,China(Grant No.182102210241)Key Projects of Science and Technology Research of Henan Provincial Department of Education,China(Grant No.18A140014)Industrial Science and Technology Research Projects of Kaifeng,Henan Province,China(Grant No.1501049)
文摘Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y2Mo3O12 ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y2Mo3O12 could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y2-x(ZnLi)xMo3O12(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn^2+ and Li+for Y^3+ in Y2Mo3O12 resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y2-x(ZnLi)xMo3O12 could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574276,51702097,and 11574083)the Program for Innovative Research Team(in Science and Technology)in University of Henan Province,China(Grant No.16IRTSTHN017)Henan Science and Technology Development Project,China(Grant No.182102210241)
文摘Low thermal expansion materials are mostly ceramics with low conductive property, which limits their applications in electronic devices. The poor conductive property of ceramic ZrV_2 O_7 could be improved by bi-substitution of Fe and Mo for Zr and V, accompanied with low thermal expansion. Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 has electrical conductivity of 8.2× 10^(-5) S/cm and 9.41× 10^(-4) S/cm at 291 K and 623 K, respectively. From 291 K to 413 K, thermal excitation leads to the increase of carrier concentration, which causes the rapid decrease of resistance. At 413–533 K, the conductivity is unchanged due to high scattering probability and a slowing increase of carrier concentration. The conductivity rapidly increases again from533 K to 623 K due to the intrinsic thermal excitation. The thermal expansion coefficient of Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 is as low as 0.72× 10^(-6 )K^(-1) at 140–700 K from the dilatometer measurement. These properties suggest that Zr_(0.1) Fe_(0.9) V_(1.1 )Mo_(0.9 )O_7 has attractive application in electronic components.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574276,51302249,and 51503185)the Doctoral Fund of the Ministry of Education of China(Grant No.20114101110003)
文摘Solid solutions of In2(1-x)(HfMg)xMo3O12 are synthesized by solid state reaction with the aim to reduce the phase transition temperature of In2Mo3O12 and improve its thermal expansion property.The effects of(HfMg)^6+ incorporation on the phase transition and thermal expansion are investigated.It is shown that the monoclinic-to-orthorhombic phase transition temperature obviously decreases and the coefficient of thermal expansion(CTE) of the orthorhombic becomes less negative and approaches to zero with increasing the content of(HfMg)^6+.A near zero thermal expansion covering the case at room temperature(RT) is achieved for the solid solutions with x ≥ 0.85,implying potential applications of this material in many fields.
基金supported by the National Natural Science Foundation of China(Grant Nos.10974183 and 11104252)the Science Fund of the Ministry of Education of China(Grant No.20114101110003)+1 种基金the Fund for Science&Technology Innovation Team of Zhengzhou City,China(Grant No.112PCXTD337)the Postdoctoral Research Sponsorship in Henan Province,China(Grant No.2011002)
文摘Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12(x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9) are synthesized, and the effects of Zr4+ and Mg2+ co-incorporation on the phase transition, thermal expansion, and Raman mode are investigated. It is found that Cr2-xZr0.5xMg0.5xMo3O12 crystallize into monoclinic structures for x 〈 1.3 and orthorhombic structures for x _〉 1.5 at room temperature. The phase transition temperature from a monoclinic to an orthorhombic structure of Cr2Mo3O12 can be reduced by the partial substitution of (ZrMg)6+ for Cr3+. The overall linear thermal expansion coefficient decreases with the increase of the (ZrMg)6+ content in an orthorhombic structure sample. The co-incorporation of Zr4+ and Mg2+ in the lattice results in the occurrence of new Raman modes and the hardening of the symmetric vibrational modes, which are attributed to the MoO4 tetrahedra sharing comers with ZrO6/MgO6 octahedra and to the strengthening of Mo-O bonds due to less electronegativities of Zr4+ and Mg2+ than Cr3+, respectively.
基金Supported by the National Science Foundation of China(Nos 10974183,11104252)the Ministry of Education of China(No 20114101110003)+1 种基金the Fund for Science&Technology Innovation Team of Zhengzhou(No 112PCXTD337)the Postdoctoral Research Sponsorship in Henan Province(No 2011002).
文摘A material with the formula ZrMgMo_(3)O_(12) having negative thermal expansion is presented and characterized.It is shown that ZrMgMo_(3)O_(12) crystallizes in an orthorhombic symmetry with space group Pnma(62)or Pna21(33)and exhibits negative thermal expansion in a large temperature range(αl=-3.8×10^(-6) K^(-1) from 300 K to 1000 K by x-ray diffraction andαl=-3.73×10^(-6) K^(-1) from 295 K to 775 K by dilatometer).ZrMgMo_(3)O_(12) remains the orthorhombic structure without phase transition or decomposition at least from 123 K to 1200 K and is not hygroscopic.These properties make it an excellent material with negative thermal expansion for a variety of applications.