It is significant for low-cost preparation of YBa2Cu3O7-δ（YBCO） coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the ...It is significant for low-cost preparation of YBa2Cu3O7-δ（YBCO） coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the present work,a distinct nucleation mechanism was proposed based on a transient liquid phase induced by the size effect as well as near-equilibrium assumption. With this scheme the nucleation of YBCO prepared by metal–organic deposition（MOD） or the physical vapor deposition BaF2 process was semi-quantitatively analyzed, revealing that the direct driving force for nucleation is YBCO supersaturation in the liquid phase. The theoretical analysis on the nucleation orientation portion is evidenced by the experimental result.展开更多
Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDX and AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observed for 0.4 mol Ag doped YBCO.AES analysis indicated tha...Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDX and AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observed for 0.4 mol Ag doped YBCO.AES analysis indicated that Ag segregated on surface of YBCO and resulted in decrease of YBCO-metal lead resistance.In addition,solution and segregation of Ag as elemental state were often appeared on interfaces and surfaces of high temperature annealed YBCO,whether elemental Ag or compound Ag_2O and AgNO_3 adopted as doping material.展开更多
YBa2Cu3O7-x(YBCO) thin film has been epitaxially deposited on (1120) sapphire with Y2O3-stabilized ZrO2 (YSZ) buffer layer and shown a high critical current density Jc of 1. 6×106A/cm2 at 77 K in zero magnetic fi...YBa2Cu3O7-x(YBCO) thin film has been epitaxially deposited on (1120) sapphire with Y2O3-stabilized ZrO2 (YSZ) buffer layer and shown a high critical current density Jc of 1. 6×106A/cm2 at 77 K in zero magnetic field. The orientation relationship of the multilayer film superconductor has been determined. The(001) plane of the YBCO film is parallel to the(100) surface of the YSZ intermediate layer. YSZ buffer layer with(100) preferred orientation is about 20 nm thick and contains element Ba, due to out-diffusion of Ba from YBCO layer. The(100) preferred orientation of YSZ buffer permits the growth of high quality YBCO thin film. Y2BaCuO5 precipitates with small size distribute uniformly in the YBCO thin film and it is favourable to raise critical current density Jc.展开更多
The patterning technologies and process order of high Tc(86K) super-conducting film bolometers have been studied. After the deposition, a conventional lithographic process was used to pattern the films with aqueous so...The patterning technologies and process order of high Tc(86K) super-conducting film bolometers have been studied. After the deposition, a conventional lithographic process was used to pattern the films with aqueous solution of HCl, and then the films were transferred into a tube furnace for annealing to form superconducting film. It eliminates the degradation of patterning process. The bolometric responsivity of approximately 34. 32 V/W is measured, and the detectivity is greater than 1. 62× 108cm · Hz1/2 · W-1, the noise equivalent powers NEP is 2. 1×10-9W.展开更多
By means of X-ray diffraction investigations and electric resistivity measurements the tempera- ture dependence of phase structure and supercon- ductivity in YBa_2Cu_3O_(7_x) over the temperature range of 20℃-950℃ h...By means of X-ray diffraction investigations and electric resistivity measurements the tempera- ture dependence of phase structure and supercon- ductivity in YBa_2Cu_3O_(7_x) over the temperature range of 20℃-950℃ have been studied.The lattice parameters a,b and c as well as conductivity as a function of annealing temperatures can be roughly divided into three zones which are superconductive orthorhombic structure 1(a<b(?)c/3) at 20℃-500℃,normal conductive orthorhombic structure 2(a<b<c/3)from 550℃ to about 750℃ and semiconductive-like tetragonal structure (a=b<c/3)from about 800℃ to 950℃.However, the boundaries of the three zones is not much distinctive because there is a continuous transi- tion from the orthorhombic to tetragonal struc- ture.Furthermore,the processes of orthorhom- bic-tetragonal transition in the range of 350℃-950℃ are not only continuous but also reversible.The isothermal transition of orthorhombic 2 to orthorhombic 1 occurs at 350℃-500℃,while the maximum rate of transition and high T_c superconductivity can be obtained at about 460℃.This process of isothermal transition depends on the ordering of oxygen atoms or vacancies and the thermodynamic equilibrium to allow the oxygen diffusion.展开更多
The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relati...The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relationship between frontier orbitals and organic chemical reactions. Based on the above results. properexperimental conditions for the preparation of homogeneous ultra-purity. submicro high-T_cYBa_2Cu_3O_(7-δ) superconducting powders are proposed.展开更多
The quantum chemical calculations of cluster YBa_2Cu_3O_7 considering all electrons have been per- formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potential is propos...The quantum chemical calculations of cluster YBa_2Cu_3O_7 considering all electrons have been per- formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potential is proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtain a relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.The suggestions that there exists a covalent bonding complex,[CuO_2-O-CuO-O-Cu_2]^(6,8-),in the cell unit of the crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys- tal lattice are offered based on the chemical bonding characteristics from the calculated results.The important contribution of the apical oxygen to superconductivities is emphasized as well.展开更多
This paper reports the experimental results of the investigation on elemental substitution effects in YBa_2Cu_3O_(7-δ) and the new physical ideas deduced comprehensively. It is shown that all the orthorhombic crystal...This paper reports the experimental results of the investigation on elemental substitution effects in YBa_2Cu_3O_(7-δ) and the new physical ideas deduced comprehensively. It is shown that all the orthorhombic crystalline structure, oxygen content, oxidation valence of Cu atoms, and metal-semiconductor (insulator) transition are only the extrinsic factors deter mining the T_c of the systems, and there are two mechanisms of substitution effects, namely the mechanism of the substitution effects outside the CuO_2 planes and that within the CuO_2 planes. We suggest that the mobile carrier concentration and the dynamic, short-range antiferromagnetic correlation between Cu(2) atoms on the CuO_2 planes are the two intrinsic factors determining the high T_c superconductivity.展开更多
Microstructure of high-quality YBa2Cu3O7-x superlattices has been investigated using high-resolution transmission electron microscope (HRTEM). The observations revealed that the superlattioes had atomic sharp interfac...Microstructure of high-quality YBa2Cu3O7-x superlattices has been investigated using high-resolution transmission electron microscope (HRTEM). The observations revealed that the superlattioes had atomic sharp interfaces between YBCO and PrBCO layers without interdiffusion. But undulations and. steps of the layer thickness existed in the specimen. An intermediate layer about 1 nm in thickness with many defects, which was caused by the surface steps and dislocations at SrTiO3 substrate surface, was observed at the film-substrate interfaces. However, the films did not have large extended defects beyond several unit cells. The results suggested that when studying the two-dimensional transport properties and superconducting mechanism of YACO using YBCO/PrBCO superlattioes or ultra-thin YBCO films, the influence of the micro-structural elements must be taken into account.展开更多
LaMnO_(3)(LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y<sub>2</sub>O<sub>3</sub>/Haste...LaMnO_(3)(LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y<sub>2</sub>O<sub>3</sub>/Hastelloy tape. The effects of the surface roughness of LMO on the crystallization, texture and superconducting properties of Yba<sub>2</sub>Cu<sub>3</sub>O<sub>7?δ </sub> (YBCO) films were systematically investigated. The crystallization and epitaxial texture of resulting YBCO film are significantly improved with the surface roughness of LMO decreasing from 7.0 to 1.3nm. High-performance YBCO-coated conductors could be achieved if surface roughness of LMO cap layer is well controlled.展开更多
It is well known that for technological application,a great effort has been done to enchance Jvalue ofsuperconducting YBaCuO sintered bulk.Except oxygen content,the main problem for increasing critical cur-rent densit...It is well known that for technological application,a great effort has been done to enchance Jvalue ofsuperconducting YBaCuO sintered bulk.Except oxygen content,the main problem for increasing critical cur-rent density Jis to eliminate the weak link and to control crystallographic anisotropy.It is necessary tomake YBaCuO superconducting bulk have a strong texture with C-axis orientation.Since Jin et al.has suc-展开更多
SHI irradiation method may be another method except in-situ growth techniques to generate one-dimensional defects in YBCO(YBa_(2)Cu_(3)O_(7)-x)films and has already been studied since 1990[1].
基金Project supported by the Science and Technology Commission of Shanghai Municipality,China(Grant Nos.13111102300 and 11dz1100302)the National Natural Science Foundation of China(Grant Nos.11174193 and 51202141)+1 种基金the National Basic Research Program of China(Grant Nos.2011CBA00105)the Science and Technology Commission of Shanghai Municipality,China(Grant No.14DZ2260700)
文摘It is significant for low-cost preparation of YBa2Cu3O7-δ（YBCO） coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the present work,a distinct nucleation mechanism was proposed based on a transient liquid phase induced by the size effect as well as near-equilibrium assumption. With this scheme the nucleation of YBCO prepared by metal–organic deposition（MOD） or the physical vapor deposition BaF2 process was semi-quantitatively analyzed, revealing that the direct driving force for nucleation is YBCO supersaturation in the liquid phase. The theoretical analysis on the nucleation orientation portion is evidenced by the experimental result.
文摘Interfaces and surfaces of YBa_2Cu_3O_(7-x)(YBCO)-Ag have been studied by SEM-EDX and AES.No effect of Ag on 123 structure in X-ray diffraction pattern was observed for 0.4 mol Ag doped YBCO.AES analysis indicated that Ag segregated on surface of YBCO and resulted in decrease of YBCO-metal lead resistance.In addition,solution and segregation of Ag as elemental state were often appeared on interfaces and surfaces of high temperature annealed YBCO,whether elemental Ag or compound Ag_2O and AgNO_3 adopted as doping material.
文摘YBa2Cu3O7-x(YBCO) thin film has been epitaxially deposited on (1120) sapphire with Y2O3-stabilized ZrO2 (YSZ) buffer layer and shown a high critical current density Jc of 1. 6×106A/cm2 at 77 K in zero magnetic field. The orientation relationship of the multilayer film superconductor has been determined. The(001) plane of the YBCO film is parallel to the(100) surface of the YSZ intermediate layer. YSZ buffer layer with(100) preferred orientation is about 20 nm thick and contains element Ba, due to out-diffusion of Ba from YBCO layer. The(100) preferred orientation of YSZ buffer permits the growth of high quality YBCO thin film. Y2BaCuO5 precipitates with small size distribute uniformly in the YBCO thin film and it is favourable to raise critical current density Jc.
文摘The patterning technologies and process order of high Tc(86K) super-conducting film bolometers have been studied. After the deposition, a conventional lithographic process was used to pattern the films with aqueous solution of HCl, and then the films were transferred into a tube furnace for annealing to form superconducting film. It eliminates the degradation of patterning process. The bolometric responsivity of approximately 34. 32 V/W is measured, and the detectivity is greater than 1. 62× 108cm · Hz1/2 · W-1, the noise equivalent powers NEP is 2. 1×10-9W.
文摘By means of X-ray diffraction investigations and electric resistivity measurements the tempera- ture dependence of phase structure and supercon- ductivity in YBa_2Cu_3O_(7_x) over the temperature range of 20℃-950℃ have been studied.The lattice parameters a,b and c as well as conductivity as a function of annealing temperatures can be roughly divided into three zones which are superconductive orthorhombic structure 1(a<b(?)c/3) at 20℃-500℃,normal conductive orthorhombic structure 2(a<b<c/3)from 550℃ to about 750℃ and semiconductive-like tetragonal structure (a=b<c/3)from about 800℃ to 950℃.However, the boundaries of the three zones is not much distinctive because there is a continuous transi- tion from the orthorhombic to tetragonal struc- ture.Furthermore,the processes of orthorhom- bic-tetragonal transition in the range of 350℃-950℃ are not only continuous but also reversible.The isothermal transition of orthorhombic 2 to orthorhombic 1 occurs at 350℃-500℃,while the maximum rate of transition and high T_c superconductivity can be obtained at about 460℃.This process of isothermal transition depends on the ordering of oxygen atoms or vacancies and the thermodynamic equilibrium to allow the oxygen diffusion.
文摘The structural characteristics of different alkoxides of Y. Ba and Cu are studied with quantum chemi-cal CNDO /2 calculations. The relative hydrolysis rate coefficients k_M of them are obtained according tothe relationship between frontier orbitals and organic chemical reactions. Based on the above results. properexperimental conditions for the preparation of homogeneous ultra-purity. submicro high-T_cYBa_2Cu_3O_(7-δ) superconducting powders are proposed.
文摘The quantum chemical calculations of cluster YBa_2Cu_3O_7 considering all electrons have been per- formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potential is proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtain a relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.The suggestions that there exists a covalent bonding complex,[CuO_2-O-CuO-O-Cu_2]^(6,8-),in the cell unit of the crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys- tal lattice are offered based on the chemical bonding characteristics from the calculated results.The important contribution of the apical oxygen to superconductivities is emphasized as well.
基金Project supported by the Combined Centre of Research and Development of Superconduction Technology and the National Natural Science Foundation of China.
文摘This paper reports the experimental results of the investigation on elemental substitution effects in YBa_2Cu_3O_(7-δ) and the new physical ideas deduced comprehensively. It is shown that all the orthorhombic crystalline structure, oxygen content, oxidation valence of Cu atoms, and metal-semiconductor (insulator) transition are only the extrinsic factors deter mining the T_c of the systems, and there are two mechanisms of substitution effects, namely the mechanism of the substitution effects outside the CuO_2 planes and that within the CuO_2 planes. We suggest that the mobile carrier concentration and the dynamic, short-range antiferromagnetic correlation between Cu(2) atoms on the CuO_2 planes are the two intrinsic factors determining the high T_c superconductivity.
文摘Microstructure of high-quality YBa2Cu3O7-x superlattices has been investigated using high-resolution transmission electron microscope (HRTEM). The observations revealed that the superlattioes had atomic sharp interfaces between YBCO and PrBCO layers without interdiffusion. But undulations and. steps of the layer thickness existed in the specimen. An intermediate layer about 1 nm in thickness with many defects, which was caused by the surface steps and dislocations at SrTiO3 substrate surface, was observed at the film-substrate interfaces. However, the films did not have large extended defects beyond several unit cells. The results suggested that when studying the two-dimensional transport properties and superconducting mechanism of YACO using YBCO/PrBCO superlattioes or ultra-thin YBCO films, the influence of the micro-structural elements must be taken into account.
基金financially supported by the National Science Foundation of China(No.91421110)the National High Technology Research and Development Program of China(No.2014AA032702)+2 种基金the National Basic Research Program of China(No.2015CB358600)Sichuan Youth Science and Technology Innovation Research Team Fund(No.2011JTD0006)Sichuan Provincial Fund for Distinguished Young Academic and Technology Leaders(No.2014JQ0011)
文摘LaMnO_(3)(LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y<sub>2</sub>O<sub>3</sub>/Hastelloy tape. The effects of the surface roughness of LMO on the crystallization, texture and superconducting properties of Yba<sub>2</sub>Cu<sub>3</sub>O<sub>7?δ </sub> (YBCO) films were systematically investigated. The crystallization and epitaxial texture of resulting YBCO film are significantly improved with the surface roughness of LMO decreasing from 7.0 to 1.3nm. High-performance YBCO-coated conductors could be achieved if surface roughness of LMO cap layer is well controlled.
文摘It is well known that for technological application,a great effort has been done to enchance Jvalue ofsuperconducting YBaCuO sintered bulk.Except oxygen content,the main problem for increasing critical cur-rent density Jis to eliminate the weak link and to control crystallographic anisotropy.It is necessary tomake YBaCuO superconducting bulk have a strong texture with C-axis orientation.Since Jin et al.has suc-
基金National Natural Science Foundation of China(11675233,11690041,11705246)CAS“Light of West China”Program and Natural Science Foundation of Gansu Province(18JR3RA392)。
文摘SHI irradiation method may be another method except in-situ growth techniques to generate one-dimensional defects in YBCO(YBa_(2)Cu_(3)O_(7)-x)films and has already been studied since 1990[1].
