THERMAL-CONDUCTIVITY OF YBCO AND THERMAL CONDUCTANCE AT YBCO RUBY BOUNDARY .2. HYSTERESIS BEHAVIOR BETWEEN 40-K AND 230-K

The thermal conductivity, k, of YBCO superconducting oxides and the thermal conductance, R(b)-1, at the YBCO/ruby boundary have been simultaneously measured during a heating cycle using a joint experimental set-up and a steady state method. The measurements were carried out in the temperature range 10 - 260 K. Thermal hysteresis of both the thermal conductivity and thermal boundary conductance have been observed within the temperature interval 40 - 230 K. Some speculations and substantiations using other methods of measurement are offered in order to explain the observed behaviour of k(T) and R(b)-1(T).