Thermodynamic Properties of Nd_1+xBa_2–x­Cu₃O_y Compounds and Their Application for Optimizing the Synthesis of Superconducting Materials

Abstract

The standard enthalpies of formation from oxides of Nd 1+x Ba 2-x Cu 3 O y , where x = 0-0.8 and y = 6.65-7.24, were determined by using dissolution enthalpies of these compounds measured by solution calorimetry. The temperature dependence of the heat capacity of NdBa 2 Cu 3 O 6.87 was measured over the range 5-320 K by adiabatic calorimetry. (0)]/T, were calculated by using the temperature dependence of C p in the interval 0-320 K. The heat The absolute entropy, S°(T), the enthalpy of heating, H°(T K) -H°(0 K), and the reduced Gibbs energy, Φ°(T) = S°(T) -[H°(T) -H°