ON THE EFFECT OF CD DOPING AND CD-LA CODOPING IN YBA2CU3O7-DELTA

Phase stability and superconducting properties of ceramic samples of n ominal composition Y1-xCdxBa2Cu3O7-delta (Cd doped) and Y1-xCdxBa2-xLa xCu3O7-delta (Cd-La codoped) were investigated for 0.0 less than or eq ual to x less than or equal to 1.0. The formation of secondary phases was observed for all samples containing Cd. The impurity peaks in the XRD patterns of Cd doped samples with x less than or equal to 0.15 dis appeared upon annealing above 800 degrees C in argon and appeared on r e-annealing above 700 degrees C in oxygen. However, the disappearance of the impurity peaks did not ascertain single phase formation. The el ectrical properties of Cd doped and Cd-La codoped samples are presente d. Semi-quantitative energy dispersive X-ray (EDX) analyses on Y1-xCdx Ba2-xLaxCu3O7-delta samples showed that Cd substitution occurs only to a limited extent in La rich (x >0.6) samples. This partial incorporat ion of Cd appears to be related to the occupancy of La at the Y-site i n a subtle manner. It is shown that the present results on Cd doped sa mples, concerning the solubility of Cd, are in contrast with the earli er reports.