Instability and hysteresis of elastic properties of yttrium - barium high-temperature superconductor compounds

Is theoretically shown, that the existence two inequivalent metastable conditions of a sublattice of atoms O(4) (depending on temperature of a sample) conducts to changes of elastic constants of a main lattice and to a temperature hysteresis of speed of distribution of a ultrasonic wave. It explains results of experiments on ceramic samples YBa2Cu3O(7-δ), where a hysteresis of longitudinal and cross speeds of a ultra sound as function of temperature in an interval 60-270 K was observed. On the other hand, the thermal hysteresis in these connections is also explained by bistable behaviour of a oxygen sublattice of apex atoms. Therefore a temperature interval of a hysteresis in all cases practically identical. 12 refs., 3 figs