XRD, magnetic and EPR studies of the mixed phase La0.5Gd0.5Ba2Cu3Oy high-T-
c superconductor after prolonged (one year) "aging" at room temperature are
reported. Within this time period a pronounced change of the superconducti
ng behavior and the homogeneity of the diamagnetic shielding signal accompa
nied by substantial structural changes, reduction of the impurity phase BaC
uO2+x and increase of the EPR spectrum's intensity of Cu2+ magnetic defects
is detected. The "aging" effects are related to strain-relaxation taking p
lace during room temperature annealing that induces the formation of Cu2+ d
efect centers.