The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 parti...The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 particles in powder melting processed samples. The formation of round Y2BaCuO5 phase is due to relative content of each constitution of precursor powders in powder melting process. For powder melting process, the excessive liquid phase is eliminated, which restrains the preferred growth of Y2BaCuO5 particles.展开更多
The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymeri...The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.展开更多
YBa2Cu3O7-δ-Agx composite superconductors were prepared by hybrid sintering process using YBa2Cu3O7-δ-Agx ultrafine powder and Ag2O finepower, which were prepared by sol-gel process and precipitation process respect...YBa2Cu3O7-δ-Agx composite superconductors were prepared by hybrid sintering process using YBa2Cu3O7-δ-Agx ultrafine powder and Ag2O finepower, which were prepared by sol-gel process and precipitation process respectively. The effect of the Ag content on superconducting crictical transition temperature of YBa2Cu3O7-δ-Agx was not evident as long as YBa2Cu3O7-δ-Agx can form continuous network. But Ag can increase superconduction crictical current and density of the composite superconductors. The normal state (i.e. non-superconducting state at room temperature) resistivity shows a percolation threshold at 20%-30% Ag, whereas the superconducting net-work shows a percolationthreshold at 70% -80% Ag.展开更多
In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase ...In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made.The results showed that the temperature of phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu- um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5, BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling the sample.展开更多
基金Funded by the National Natural Science Foundation of China (50432050)the National High Technology Research and Development Program of China(2007AA03Z241)
文摘The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 particles in powder melting processed samples. The formation of round Y2BaCuO5 phase is due to relative content of each constitution of precursor powders in powder melting process. For powder melting process, the excessive liquid phase is eliminated, which restrains the preferred growth of Y2BaCuO5 particles.
文摘The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.
文摘YBa2Cu3O7-δ-Agx composite superconductors were prepared by hybrid sintering process using YBa2Cu3O7-δ-Agx ultrafine powder and Ag2O finepower, which were prepared by sol-gel process and precipitation process respectively. The effect of the Ag content on superconducting crictical transition temperature of YBa2Cu3O7-δ-Agx was not evident as long as YBa2Cu3O7-δ-Agx can form continuous network. But Ag can increase superconduction crictical current and density of the composite superconductors. The normal state (i.e. non-superconducting state at room temperature) resistivity shows a percolation threshold at 20%-30% Ag, whereas the superconducting net-work shows a percolationthreshold at 70% -80% Ag.
文摘In-situ HVEM observation on phase transition of the YBa_2Cu_3O_(7-x) superconducting compound in pro- cess of heating was carried out,and high temperature X-ray diffraction analysis in air and X-ray diffraction phase analysis for the sample treated in vacuum condition were made.The results showed that the temperature of phase transition is related to oxygen content in the sample and in general,is 100℃ to 120℃ lower in vacu- um condition than in air.At 320℃ to 350℃ twin bands begin to disappear,and some Cu_2O are formed on the surface of the sample and transit from orthorhombic YBa_2Cu_3O_(7-x) to arthorhombic Y_2BaCuO_5 compound. This transition was completed at about 500℃.Above 900℃,this compound consists of the Y_2BaCuO_5, BaCuO_2,Y_2O_3 and some other minor compounds.No phase transition was observed during cooling the sample.
