AN OPPOSITE BEHAVIOR OF SEMICONDUCTING AND SUPERCONDUCTING YBCO SINGLE-CRYSTAL

An opposite thermal dynamic change in superconducting and semiconducti ng cuprates of YBa2Cu3O7-x(Y-123) is observed. At 450 degrees C the su perconducting Y-123 single crystal shows an endothermal anomaly and a weight loss, while the semiconducting one shows an exothermal anomaly and weight gain. High temperature x-ray diffraction reveals that the l attice parameters of the Y-123 crystal jump significantly at this temp erature. A computer simulation demonstrates that the change of the lat tice parameters can be related with the change of the lattice energy.