EFFECT OF RE3-CONTENT IN SOME (RE)BA2CU3O7-X COMPOUNDS( ION SIZE ON THE EQUILIBRIUM OXYGEN)

Decomposition of single-phase (RE)Ba2Cu3O7-x compounds (RE = Y, Nd, Eu , Er) isothermally heated in high purity helium is examined. At each a nnealing temperature (T) an equilibrium is settled at definite content of removable oxygen (1 - X(eq))T. For each RE the latter values are m onotonically decreasing with increasing T according to a simple expone ntial relation valid for the whole decomposition range independently o f the crystallographic structure of the sample. It is shown that the c onstants entering above relation depend on (RE)3+ ionic radii only.