【摘要】 用声发射研究了高T_c超导材料YBaCuO在超导转变前的晶格不稳定性。YBaCuO正交相在T_c以上一定温区内有明显的声发射信号,经幅度分布分析表明,该声发射信号具有马氏体相变过程声发射信号的特征。在液氮温区无超导性的YBaCuO四方相在相同温度范围无活跃的声发射信号。更多还原

【Abstract】 Acoustic Emission (AE) studies on YBaCuO high-To superconducting ceramic materials have been performed to investigate the lattice instability above Tc with AE ringdown counts rate and AE amplitude distribution as well as AE waveform. The active AE signal due to the micr-ostructure modulation (or like-phase-transformation) around 130K (Tc+ 40K) was observed in YBaCuO ceramic orthorhombic phase (a≠b) which displays superconductivity at 90K.Comparing the AE amplitude distribution and riagdown count distribution of YBaCuO orthorhombic phase with those of Cu-Zn-Al shape memory alloy, the microstructure modulation in YBaCuO is shown to be some characteristic of martensitic phase transformation.Very weak AE signal was observed in YBaCuO ceramic tetragonal phase (a = b) which does not display superconductivity in liquid nitrogen temperature range.更多还原