Thermodynamics of the ( lanthanum + strontium + copper + oxygen ) high - T , superconductors I

The subambient heat capacities of three (SrO),(CuO), inter-oxide samples with Y = y = I: I = 7. y=l; and u=l. y=2, were measured as a part of an investigation into the chemical thermodynamics of the high-T, superconducting system (lanthanum + strontium + copper + oxygen). No anomalous contribution to the heat capacity was observed over the experimental region. The heat capacity of the Sr,,Cu,,O,, phase was derived from that of the mixed phase of nominal composition .Y = 1, y = 2. All samples exhibit a Debye-like behavior at low temperatures with finite linear electronic terms. Thermophysical properties at selected temperatures are presented and compared for the three compounds. The values of S, at 298.15 K for the three compounds Sr, JuI 20, Srz ,Cu, 3O. and Sr,, 3HC~2J 3H041 Jx were: 5.828 R. 5.953. R. and 6.032. R. respectively.