The addition Of Pb enhances the hightemperature stability as well as theproportion of the high Tphase in Bi-Sr-Ca-Cu-O superconductor.The sample A with nominal composi-tion of BiSrCaCuOwas synthesized bySolid state re...The addition Of Pb enhances the hightemperature stability as well as theproportion of the high Tphase in Bi-Sr-Ca-Cu-O superconductor.The sample A with nominal composi-tion of BiSrCaCuOwas synthesized bySolid state reaction.It was sintered in airat 1153K for 24h,followed by annealingat 773K for 24h and furnace-cooling.The sample B with a nominal compositionof BiPbSrCaCuOwas prepared bymixing PbO with the powder ofBiSrCaCuOwhich had been prefired at1113K for 24h,pressing,sintering at展开更多
The oxygen relief/absorption,superconduc— tivity and structure of(Bi_(1-x)Pb_x)_2Sr_2Ca_2— Cu_3O_y compounds have been studied by TGA, electrical resistance measurement and X-ray diffraction.The amount of oxygen whi...The oxygen relief/absorption,superconduc— tivity and structure of(Bi_(1-x)Pb_x)_2Sr_2Ca_2— Cu_3O_y compounds have been studied by TGA, electrical resistance measurement and X-ray diffraction.The amount of oxygen which can be re- leased and superconductivity of the compounds are correlative to Pb content.The release of oxygen in- creases when x less than 0.2 and decreases when x exceeds 0.2 with increasing x.The appropriate con- tent of Pb for superconductivity is in the range of 0.1<x<0.3,which corresponds to the relative large amount of oxygen that can be released.It is found according to electric resistance measurement that quenching is favourable to form the‘85K’phase and slow cooling the‘110K’phase.The experimen- tal results suggest that a relation exists between the superconductivity and the oxygen content in Bi sys- tem containing Pb.As the T_c of‘85K’phase de- creases and that of‘110K’phase increases with in- creasing oxygen content,it is possible that the effect of oxygen content in‘85K’phase and‘110K’ phase on the superconductivity is different.展开更多
In this research two samples of a nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Ox were prepared by the solid state reaction method, using two different routes. Codes A and B are used to refer to the two samples. In preparin...In this research two samples of a nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Ox were prepared by the solid state reaction method, using two different routes. Codes A and B are used to refer to the two samples. In preparing sample A, the standard method for calcination was used, while for sample B, the SrCO3 and CaCO3 were calcinated at 1100℃ for 3 h. Calcination was done separately on SrCO3 and CaCO3 in order to eliminate CO2. Then after mixing and grinding, the powder mixtures of Bi2O3, CuO, PbO, SrO and CaO were calcinated at 840℃ for 70 h. Also, the samples (samples C) of nominal compositions Bi1.6Pb0.4Sr2Ca2Cu3Ox+ % x Gd2O3 (% x = 0, 3, 5, 7 and 9) have been synthesized by this method. The XRD and SEM results show that addition of Gd2O3 helps to increase the amount of Bi-2212 phase, while alternative calcination process improves the formation of the Bi-2223 phase. In addition, the AC susceptibility measurements confirm the XRD and SEM results.展开更多
A modified coprecipitation process is presented based on the stoichiometry study of oxalate coprecipitation process in water medium to synthesize Bi-Pb-Sr-Ca-Cu-O multi-component powder.Its characteristic is that the ...A modified coprecipitation process is presented based on the stoichiometry study of oxalate coprecipitation process in water medium to synthesize Bi-Pb-Sr-Ca-Cu-O multi-component powder.Its characteristic is that the coprecipitation reaction takes place in a mixed solution medium composed of water and a kind of organic solvent (volume percentage 】90%).Thus,it overcomes the serious shortcoming of inability to maintain stoichiometry in Bi-system superconductor powder synthesized by water-medium coprecipitation.The effects of pH value,oxalic acid concentration and aging time on stoichiometry maintenance in precipitate are systematically studied.Bulk material made from the powder prepared by the new modified coprecipitation also shows the success of the new process.展开更多
I. INTRODUCTIONFrom the reflection-absorption spectra, Raman spectra and fluorescence spectra etc. of Y-Ba-Cu-O high T_c superconductor, much information concerning the structure of energy band, the density of states ...I. INTRODUCTIONFrom the reflection-absorption spectra, Raman spectra and fluorescence spectra etc. of Y-Ba-Cu-O high T_c superconductor, much information concerning the structure of energy band, the density of states and the electron-phonon coupling strength has been obtained. The discovery of Bi-Sr-Ca-Cu-O system indicates a new direction for the re-展开更多
There are at least three superconducting phases in the Bi-Sr-Ca-Cu-O system, Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>x</sub> （2201 phase）, Bi<sub>2</sub>Sr<sub>2<...There are at least three superconducting phases in the Bi-Sr-Ca-Cu-O system, Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>x</sub> （2201 phase）, Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>y</sub> （2212 phase） and Bi<sub>2</sub>Sr<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>z</sub> （2223 phase ）. At present, the high temperature behavior of superconducting phases has not been reported in detail. In fact, the melting process plays an important role in improving J<sub>c</sub> in oxide superconducting materials. For Bi-system, therefore, the study on high temperature behavior of the superconducting phases is important for increasing the J<sub>c</sub> values.展开更多
In the Bi-Sr-Ca-Cu-O superconductor system, two superconducting phases (85K and 105K) were found by Maeda et al. By substituting Pb, enhanced superconducting properties and structure stabilization in these compounds h...In the Bi-Sr-Ca-Cu-O superconductor system, two superconducting phases (85K and 105K) were found by Maeda et al. By substituting Pb, enhanced superconducting properties and structure stabilization in these compounds have been reported. Recently, the展开更多
文摘The addition Of Pb enhances the hightemperature stability as well as theproportion of the high Tphase in Bi-Sr-Ca-Cu-O superconductor.The sample A with nominal composi-tion of BiSrCaCuOwas synthesized bySolid state reaction.It was sintered in airat 1153K for 24h,followed by annealingat 773K for 24h and furnace-cooling.The sample B with a nominal compositionof BiPbSrCaCuOwas prepared bymixing PbO with the powder ofBiSrCaCuOwhich had been prefired at1113K for 24h,pressing,sintering at
文摘The oxygen relief/absorption,superconduc— tivity and structure of(Bi_(1-x)Pb_x)_2Sr_2Ca_2— Cu_3O_y compounds have been studied by TGA, electrical resistance measurement and X-ray diffraction.The amount of oxygen which can be re- leased and superconductivity of the compounds are correlative to Pb content.The release of oxygen in- creases when x less than 0.2 and decreases when x exceeds 0.2 with increasing x.The appropriate con- tent of Pb for superconductivity is in the range of 0.1<x<0.3,which corresponds to the relative large amount of oxygen that can be released.It is found according to electric resistance measurement that quenching is favourable to form the‘85K’phase and slow cooling the‘110K’phase.The experimen- tal results suggest that a relation exists between the superconductivity and the oxygen content in Bi sys- tem containing Pb.As the T_c of‘85K’phase de- creases and that of‘110K’phase increases with in- creasing oxygen content,it is possible that the effect of oxygen content in‘85K’phase and‘110K’ phase on the superconductivity is different.
文摘In this research two samples of a nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Ox were prepared by the solid state reaction method, using two different routes. Codes A and B are used to refer to the two samples. In preparing sample A, the standard method for calcination was used, while for sample B, the SrCO3 and CaCO3 were calcinated at 1100℃ for 3 h. Calcination was done separately on SrCO3 and CaCO3 in order to eliminate CO2. Then after mixing and grinding, the powder mixtures of Bi2O3, CuO, PbO, SrO and CaO were calcinated at 840℃ for 70 h. Also, the samples (samples C) of nominal compositions Bi1.6Pb0.4Sr2Ca2Cu3Ox+ % x Gd2O3 (% x = 0, 3, 5, 7 and 9) have been synthesized by this method. The XRD and SEM results show that addition of Gd2O3 helps to increase the amount of Bi-2212 phase, while alternative calcination process improves the formation of the Bi-2223 phase. In addition, the AC susceptibility measurements confirm the XRD and SEM results.
文摘A modified coprecipitation process is presented based on the stoichiometry study of oxalate coprecipitation process in water medium to synthesize Bi-Pb-Sr-Ca-Cu-O multi-component powder.Its characteristic is that the coprecipitation reaction takes place in a mixed solution medium composed of water and a kind of organic solvent (volume percentage 】90%).Thus,it overcomes the serious shortcoming of inability to maintain stoichiometry in Bi-system superconductor powder synthesized by water-medium coprecipitation.The effects of pH value,oxalic acid concentration and aging time on stoichiometry maintenance in precipitate are systematically studied.Bulk material made from the powder prepared by the new modified coprecipitation also shows the success of the new process.
基金Project supported by the National Natural Science Foundation of China.
文摘I. INTRODUCTIONFrom the reflection-absorption spectra, Raman spectra and fluorescence spectra etc. of Y-Ba-Cu-O high T_c superconductor, much information concerning the structure of energy band, the density of states and the electron-phonon coupling strength has been obtained. The discovery of Bi-Sr-Ca-Cu-O system indicates a new direction for the re-
基金Project supported by the National Center for R & D on superconductivity of China
文摘There are at least three superconducting phases in the Bi-Sr-Ca-Cu-O system, Bi<sub>2</sub>Sr<sub>2</sub>CuO<sub>x</sub> （2201 phase）, Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>y</sub> （2212 phase） and Bi<sub>2</sub>Sr<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>z</sub> （2223 phase ）. At present, the high temperature behavior of superconducting phases has not been reported in detail. In fact, the melting process plays an important role in improving J<sub>c</sub> in oxide superconducting materials. For Bi-system, therefore, the study on high temperature behavior of the superconducting phases is important for increasing the J<sub>c</sub> values.
文摘In the Bi-Sr-Ca-Cu-O superconductor system, two superconducting phases (85K and 105K) were found by Maeda et al. By substituting Pb, enhanced superconducting properties and structure stabilization in these compounds have been reported. Recently, the
