DEFECT THERMODYNAMICS OF (LA1-XSRX)2CUO4-DELTA SUPERCONDUCTING OXIDE

The oxygen deficit delta of (La1-xSr(x))2CuO4-delta was determined as function of oxygen partial pressure (Po2) at various temperatures. When the delta-log Po2 curve at a specified temperature was chosen as the reference and the curves for other temperatures were shifted along the abscissa, all the data points were found to form a single smooth curve (master curve). A theoretical equation providing delta as functions of Po2 and strontium content was derived by combining defect equilibrium, mass action law and site conservation condition. The calculated curve was found to be in good agreement with the master curve. The relationship between copper valence and strontium content at constant oxygen pressure and temperature was determined experimentally and compared with calculated values. Good agreement was found between them.