综合物理实验报告 北京大学物理系99级 周卓为,周良玉2003.1 指导教师:冯庆荣 Resistivity-Temperature Characteristics of Sol Gel Y Ba2 Cu3Oy Samples Synthesized in Flowing Oxygen Atmosphere The relationship of resistivity versus synthesizing temperature of sol gel YBa2Cug0, samples was studied while prepared under flowing oxygen conditions. A gh-temperature p-T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity was p 300=9.83 X109.cm at room temperature. The p-T curve also showed that the orthorhombic-tetragonal phase transformation of sol-gel YBazCu30, sample occurred at 581C as the sample in the rising temperature process, but at 613C in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods Key words: sol gel YBa2 Cu3O sample, p-T curve, resistivity, phase PACC:7470,7470R,7430 1 Introduction Many normal and superconducting properties of high Tc superconductors have been investigated and discussed, [ such as the crystallographic structure, BJ oxygen deficiency, H anisotropy, l6 magnetic properties, and the transport properties s)etc.However,the properties of high-temperature(HT) p-t curve have rarely been studied at temperatures higher than 800C or in the synthesis process. 9-151 Freitas et al 9 )measured the temperature dependence of the resistivity under several oxygen partial pressures Poz for YBa2Cu3Oy samples from room temperature to 800C. From these results they found that the ht order-disorder phase transition in the superconductor Y Ba Cu3Oy sample occurred at 685C as it was heated and cooled at a rate of 0.1k/min in Po=10 Pa. Cooke et al. found that the sulfur incorporation into YBa2 Cu3Oy was possible by diffusion in gaseous state according to their HT resistivity measurement of YBa2Cu3Oy. We found that the ht resistivity measurement of superconductors is a useful means for assessing the progress, success of any kind of ceramic superconductors, and researching the properties and the phase From our previous results it is known that the orthorhombic-tetragonal phase transition1 综合物理实验报告 北京大学物理系 99 级 周卓为，周良玉 2003.1. 指导教师：冯庆荣 Resistivity-Temperature Characteristics of Sol Gel YBa2Cu3Oy Samples Synthesized in Flowing Oxygen Atmosphere , The relationship of resistivity versus synthesizing temperature of sol gel YBa2Cu3Oy samples was studied while prepared under flowing oxygen conditions. A set of high-temperatureρ-T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity wasρ300 = 9.83 ×10-3 Ω·cm at room temperature. The ρ-T curve also showed that the orthorhombic-tetragonal phase transformation of sol-gel YBa2Cu3Oy sample occurred at 581℃ as the sample in the rising temperature process, but at 613℃ in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods. Key words: sol gel YBa2Cu3Oy sample, ρ-T curve, resistivity, phase transformation. PACC: 7470, 7470R, 7430 1. Introduction Many normal and superconducting properties of high Tc superconductors have been investigated and discussed，[1,2] such as the crystallographic structure，[3] oxygen deficiency，[4] defects，[5]anisotropy，[6] magnetic properties，[7] and the transport properties[8] etc. However, the properties of high-temperature (HT) ρ―T curve have rarely been studied at temperatures higher than 800 ℃ or in the synthesis process．[9-15] Freitas et al[9] measured the temperature dependence of the resistivity under several oxygen partial pressures Po2 for YBa2Cu3Oy samples from room temperature to 800℃. From these results they found that the HT order-disorder phase transition in the superconductor YBa2Cu3Oy sample occurred at 685℃ as it was heated and cooled at a rate of 0.1K/min in Po2=105 Pa. Cooke et al．[10] found that the sulfur incorporation into YBa2Cu3Oy was possible by diffusion in gaseous state according to their HT resistivity measurement of YBa2Cu3Oy. We found that the HT resistivity measurement of superconductors is a useful means for assessing the progress, success of any kind of ceramic superconductors, and researching the properties and the phase formation．[11-16] From our previous results[11] it is known that the orthorhombic-tetragonal phase transition