Thermal conductivity of the Y-Ba-Cu-O tetragonal structure: phase transitions and hysteresis behaviour

Abstract

The authors present results of precise measurements of the thermal conductivity lambda of a non-superconducting sample of Y-Ba-Cu-O in the temperature range 1-300 K. Heating and cooling curves of lambda (T) exhibited clear hysteresis effects between 80 and 240 K, not previously reported. The temperatures at which the thermal conductivity anomalies appear were the same or close to those at which other anomalies were observed in superconducting samples. The results can be explained qualitatively if one assumes that the 1:2:3 phase is a spinodal decomposition mixture of two phases with different stoichiometry with respect to oxygen content and that a change in lattice dimensions takes place at about 80 K.