Han ZHANG and Qingrong FENG (Dept. of Physics
,
Peking University
,
Beijing 100871
,
China)Y.Zhao(School of Materials Science and Engineering
,
University of New South Wales
,
Sydney 2052
,
NSW
,
Australia)F.Ritter and W.Assmus (Physikalisches Institut
,
J.W.Goet
材料科学技术（英）
Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.
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