NONSTOICHIOMETRY AND DECOMPOSITION OF LA1-ZCU3OY AND LA4BACU5O13-W(ZBA2)

The temperature (T, K) and oxygen pressure (p(O2), Pa) dependence of o xygen content in La1+zBa2-zCu3Oy (123) and La4BaCu5O13-w (415) were de termined over the ranges 10 Pa to 0.1 MPa O2, 0.0 less-than-or-equal-t o z less-than-or-equal-to 0.7 and 523 less-than-or-equal-to T less-tha n-or-equal-to 1223 K. The data for each phase were correlated with che mical thermodynamic representations. For La1+zBa2-zCu3Oy, the T-z-y-p( O2) behavior was modeled as a solution of LaBa2Cu3O7-x and 415. The ex perimental data demonstrated 7-x values < 6 at high temperatures, whil e they exceeded 6.99 only at temperatures approaching ambient at 0.1 M Pa O2. These two characteristics are not known to occur in the other l anthanide and Y analogues. The T-z-p(O2) dependence of high-temperatur e decomposition was determined and, in conjunction with X-ray analysis , permitted construction of the phase diagram lying between LaBa2Cu3O7 -x and 415. Effects of residual carbonate content were also determined .