The thermodynamic characteristics of NdBa2Cu3O7-δ

The enthalpies of solution of Nd2O3, BaCO3, CuO, and NdBa2Cu3O7-delta were measured by solution calorimetry at 323.15 K. The results were used to calculate the enthalpies of two different reactions with the participation of the NdBn2Cu3O7-delta phase [Delta H-r degrees (323.15 K)] and the enthalpies of formation of NdBa2Cu3O7-delta [Delta H-f degrees (323.15 K)] from different initial components including monoatomic gases. The heat capacities (C(p)degrees) of NdBa2Cu3O6.98 were measured in the temperature range 100-320 K. The C(p)degrees values were used to calculate the Delta H-r degrees (T) and Delta H-f degrees (T) thermodynamic functions in the temperature range 295.15-123.15 K. The NdBa2Cu3O6.98 compound was found to be thermodynamically stable with respect to the 0.5Nd(2)O(3) + CuO + 2BaCuO(2) mixture in the temperature range 298.15-323.15 K. The Gibbs energies and the entropies of reactions with the participation of the Nd123 phase were calculated.