Low temperature heat capacities and thermodynamic functions of Tl 2Ba 2CaCu 2O y

Abstract

The heat capacity of the high temperature superconductor Tl 2Ba 2CaCu 2O y was measured by adiabatic calorimetry between 7 and 300 K. The sample was carefully synthesized by a method of powder calcination, and the properties were characterized and evaluated by X-ray powder diffraction, electrical resistivity and magnetic susceptibility measurements. The values of enthalpy, entropy and Gibbs energy were calculated from the heat capacity data. An anomaly due to the superconducting phase transition at 102 K was analyzed in terms of a fluctuation effect and the distribution of T c The effect of thallium deficiency on the superconducting phase transition was also examined.