Li Li-Ping

Thermal expansion coefficient of single phase superconductor YBa2Cu3O7-δ

The thermal expansion coefficient of single phase superconductor YBa2Cu3O7-δ was measured by the method of differential parallelplate capacitance. An obvious decrease of volume near 205K and a small jump of the thermal expansion coefficient at Tc were observed. The pressure effect was also estimated.

The structure phase transition of the quenched YBa2Cu3O7−y with tetragonal phase

The single (123) phase of Y-Ba-Cu oxides with T-phase structure was prepared using the air-quenching technique. From the measurements of electrical resistance, thermal expansion coefficience, specific heat, ac susceptibility and XRD, it is the first time to find the existance of a structure phase transition. It is suggested to be a structure phase transition from Y-phase to O-phase. The explanation for low Tc in this system is also proposed in this paper.