Ⅰ. INTRODUCTIONSince the discovery of the BiSrCaCuO superconductor by Maeda et al., it has been well known that there are at least three superconducting phases: the 2201, 2212 and 2223 phases with the transition temp...Ⅰ. INTRODUCTIONSince the discovery of the BiSrCaCuO superconductor by Maeda et al., it has been well known that there are at least three superconducting phases: the 2201, 2212 and 2223 phases with the transition temperature T<sub>c</sub> of 7 K, 85 K and 110 K respectively in the Bibased system. T<sub>c</sub> is proportional to the number of the Cu-O<sub>2</sub> plane in half cell for展开更多
In this study, the effects of Nb substitution on the Bi-based superconducting materials have been investigated. The X-ray diffraction measurement indicated coexistence of Bi-2212, Bi-2223 phases and some impurity phas...In this study, the effects of Nb substitution on the Bi-based superconducting materials have been investigated. The X-ray diffraction measurement indicated coexistence of Bi-2212, Bi-2223 phases and some impurity phases of CuO, CuNb2O6, CaNb2O6, CaCuO2, and Sr5Nb5O16. With increasing Nb content, impurity phases consistent with the Nb element appeared in the samples. Also with increasing Nb content, the Bi-2223 phase of samples gradually was decreased and in contrast, the Bi-2212 phase was increased. From the SEM, results have been seen that with increasing of Nb contents, the crystal structure of the samples was slightly changed because of the disrupted grain growth. From the electrical resistivity measurements, it has been found that with increasing of Nb contents, critical temperature decreases and the superconducting transition width (ΔT) increases. Estimated critical current density showed that Jc decreases with increasing Nb content, as expected.展开更多
Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)(Bi‐2212)superconducting round wires exhibited great potential for use in high‐field applications.The purity of the precursor powders is critical for the transport current of the wires.Ho...Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)(Bi‐2212)superconducting round wires exhibited great potential for use in high‐field applications.The purity of the precursor powders is critical for the transport current of the wires.However,the role of the residual secondary phase in the precursor powders is not fully understood.Here,the origin of the secondary phase was investigated in precursor powders that were prepared using ultrasonic spray pyrolysis(USP)and calcination processing.The microstructure and phase evolution of the precursor powders during the crystallization process were analyzed.Moreover,the effects that the residual secondary phase has on melting behavior,morphology properties,and the supercurrent flow of Bi‐2212 multi‐filamentary wires are systematically discussed.The residual secondary phase in the filament caused further crystallization,and this led to the formation of more and larger Bi‐2201 grains at the onset of the melting process.The poor microstructure and low critical current of the final Bi‐2212 wires can be attributed to the presence of the residual copper‐rich phase.Bi‐2212 wires that were prepared with fully crystallized powders had a high critical current density(J_(c))of 6773 A/mm^(2) at 4.2 K,self‐field.It was revealed that control of the secondary phases in precursor powders is greatly significant for achieving superior values of J_(c).展开更多
Laying emphasis on the preparation of Bi based 2212 single phase superconducting powder, some technological parameters, which effect the single phase degree and uniformity of powder, such as prebaking, sintering and ...Laying emphasis on the preparation of Bi based 2212 single phase superconducting powder, some technological parameters, which effect the single phase degree and uniformity of powder, such as prebaking, sintering and heat treatment were investigated and discussed. Ensuring the powder T c at 83～85 K, the crucial impurity carbon was reduced to 0.03% and less. Adopting uncommon technique made the powder size to micrometer level, meanwhile the superconducting performance of the powder was unchanged. The fine superconducting powder was characterized. This process of Bi based 2212 superconducting powder was successful.展开更多
This paper have made a systematic study of the superconducting Bi-2212 phase transition temperature, which has a transition temperature (Tc) around 80-93 K, and depends on precise control of synthesis conditions, main...This paper have made a systematic study of the superconducting Bi-2212 phase transition temperature, which has a transition temperature (Tc) around 80-93 K, and depends on precise control of synthesis conditions, mainly including heat treatment parameters, oxygen partial pressure, and annealing temperature. Partial melting of the sample during preparation helps to raise its Tc. To elucidate the origin of this strong effect, the samples were heated with different melting process. The rapid changes in Tc value are associated with small changes in oxygen content, which depends on the annealing temperature and the oxygen partial pressure. We have optimized the above mentioned parameters for Bi-2212 film, and Tconset was improved to 93 K.展开更多
A reactive co-deposition processing for obtaining high-quality single-phase Bi2Sr2Cax-1CuxOy （Bi2212） thin films has been investigated using molecular beam epitaxy （MBE） with 2.7 ×10^-3pa ozone gas introducti...A reactive co-deposition processing for obtaining high-quality single-phase Bi2Sr2Cax-1CuxOy （Bi2212） thin films has been investigated using molecular beam epitaxy （MBE） with 2.7 ×10^-3pa ozone gas introduction for oxidation. The thin films with a constant composition of almost 2 ： 2 ： 1 ： 2 were designed to be fabricated at the substrate temperature between 675 and 780℃, the substrate temperature dependence of the surface morphology and the emergence phases were investigated in detail. A noticeable result is that the distribution of Cu element in the thin films is sensitively changed with the substrate temperature. At 750℃ it is inclined to locate in the periphery of each grain through the diffusion process. At 780℃ the Cu-compositional fluctuation brought around the dendritic crystal growth in the thin films. Below 705℃, the Bi2212 single-phase cannot be achieved in the thin films.展开更多
Ⅰ. INTRODUCTIONX. D. Xiang et al. have reported the preliminary structural characteristics of the iodine intercalated Bi_2Sr_2Ca_1Cu_2O_y high T_c superconductors. The cell dimension along c direction is expanded fro...Ⅰ. INTRODUCTIONX. D. Xiang et al. have reported the preliminary structural characteristics of the iodine intercalated Bi_2Sr_2Ca_1Cu_2O_y high T_c superconductors. The cell dimension along c direction is expanded from 30.80 to 37.78 after iodine is intercalated. They suggested that an iodinelayer addition with 3.5 thickness is inserted into the host crystal perpendicular to c direction. The transition temperature of the host superconductor is ranged from 82 to 90 K.展开更多
基金National Natural Science Foundation of China(51902267)Shaanxi Province Key Research and Development Program(2022GY-391,2020ZDZX04-04-02)+1 种基金National Key Project of Magneto Constrained Fusion Energy Development Program(2017YFE0301402)Natural Science Foundation of Shaanxi Province(2020JM-648)。
文摘Ⅰ. INTRODUCTIONSince the discovery of the BiSrCaCuO superconductor by Maeda et al., it has been well known that there are at least three superconducting phases: the 2201, 2212 and 2223 phases with the transition temperature T<sub>c</sub> of 7 K, 85 K and 110 K respectively in the Bibased system. T<sub>c</sub> is proportional to the number of the Cu-O<sub>2</sub> plane in half cell for
文摘In this study, the effects of Nb substitution on the Bi-based superconducting materials have been investigated. The X-ray diffraction measurement indicated coexistence of Bi-2212, Bi-2223 phases and some impurity phases of CuO, CuNb2O6, CaNb2O6, CaCuO2, and Sr5Nb5O16. With increasing Nb content, impurity phases consistent with the Nb element appeared in the samples. Also with increasing Nb content, the Bi-2223 phase of samples gradually was decreased and in contrast, the Bi-2212 phase was increased. From the SEM, results have been seen that with increasing of Nb contents, the crystal structure of the samples was slightly changed because of the disrupted grain growth. From the electrical resistivity measurements, it has been found that with increasing of Nb contents, critical temperature decreases and the superconducting transition width (ΔT) increases. Estimated critical current density showed that Jc decreases with increasing Nb content, as expected.
基金supported by the National Key R&D Program of China(2021YFB3800201)the National Science Fund Program of China(No.51777172,51902267)the Natural Science Basic Research Plan in Shaanxi Province(No.2022GY‐392,2021JQ‐884).
文摘Bi_(2)Sr_(2)CaCu_(2)O_(8+δ)(Bi‐2212)superconducting round wires exhibited great potential for use in high‐field applications.The purity of the precursor powders is critical for the transport current of the wires.However,the role of the residual secondary phase in the precursor powders is not fully understood.Here,the origin of the secondary phase was investigated in precursor powders that were prepared using ultrasonic spray pyrolysis(USP)and calcination processing.The microstructure and phase evolution of the precursor powders during the crystallization process were analyzed.Moreover,the effects that the residual secondary phase has on melting behavior,morphology properties,and the supercurrent flow of Bi‐2212 multi‐filamentary wires are systematically discussed.The residual secondary phase in the filament caused further crystallization,and this led to the formation of more and larger Bi‐2201 grains at the onset of the melting process.The poor microstructure and low critical current of the final Bi‐2212 wires can be attributed to the presence of the residual copper‐rich phase.Bi‐2212 wires that were prepared with fully crystallized powders had a high critical current density(J_(c))of 6773 A/mm^(2) at 4.2 K,self‐field.It was revealed that control of the secondary phases in precursor powders is greatly significant for achieving superior values of J_(c).
文摘Laying emphasis on the preparation of Bi based 2212 single phase superconducting powder, some technological parameters, which effect the single phase degree and uniformity of powder, such as prebaking, sintering and heat treatment were investigated and discussed. Ensuring the powder T c at 83～85 K, the crucial impurity carbon was reduced to 0.03% and less. Adopting uncommon technique made the powder size to micrometer level, meanwhile the superconducting performance of the powder was unchanged. The fine superconducting powder was characterized. This process of Bi based 2212 superconducting powder was successful.
文摘This paper have made a systematic study of the superconducting Bi-2212 phase transition temperature, which has a transition temperature (Tc) around 80-93 K, and depends on precise control of synthesis conditions, mainly including heat treatment parameters, oxygen partial pressure, and annealing temperature. Partial melting of the sample during preparation helps to raise its Tc. To elucidate the origin of this strong effect, the samples were heated with different melting process. The rapid changes in Tc value are associated with small changes in oxygen content, which depends on the annealing temperature and the oxygen partial pressure. We have optimized the above mentioned parameters for Bi-2212 film, and Tconset was improved to 93 K.
文摘A reactive co-deposition processing for obtaining high-quality single-phase Bi2Sr2Cax-1CuxOy （Bi2212） thin films has been investigated using molecular beam epitaxy （MBE） with 2.7 ×10^-3pa ozone gas introduction for oxidation. The thin films with a constant composition of almost 2 ： 2 ： 1 ： 2 were designed to be fabricated at the substrate temperature between 675 and 780℃, the substrate temperature dependence of the surface morphology and the emergence phases were investigated in detail. A noticeable result is that the distribution of Cu element in the thin films is sensitively changed with the substrate temperature. At 750℃ it is inclined to locate in the periphery of each grain through the diffusion process. At 780℃ the Cu-compositional fluctuation brought around the dendritic crystal growth in the thin films. Below 705℃, the Bi2212 single-phase cannot be achieved in the thin films.
文摘Ⅰ. INTRODUCTIONX. D. Xiang et al. have reported the preliminary structural characteristics of the iodine intercalated Bi_2Sr_2Ca_1Cu_2O_y high T_c superconductors. The cell dimension along c direction is expanded from 30.80 to 37.78 after iodine is intercalated. They suggested that an iodinelayer addition with 3.5 thickness is inserted into the host crystal perpendicular to c direction. The transition temperature of the host superconductor is ranged from 82 to 90 K.
基金National Natural Science Foundation of China(51472206)National ITER Program of China(2013GB110001)National Key Research and Development Program of China(2017YFB0902303)。
