Positron annihilation studies in high Tc superconductor YBa2Cu3CdxOy (x=0, 0.05)

Positron lifetime and Doppler broadening of the annihilation line measurements were performed in high Tc superconducting samples YBa2Cu3CdxOy, x=0, 0.05 and 6.9<y<7, as a function of temperature in the region of 14-300 K. It was found that the positron lifetime and the S parameter values are lower in the Cd doped sample than those in the undoped one. It was also observed that the positron annihilation parameters show similar temperature dependence for the undoped and Cd doped samples. We conclude that the Cd doping in high Tc superconductor YBa2Cu3CdxOy, 6.9<y<7 fills defects associated with oxygen vacancies probably in oxygen deficient regions which can trap positrons. (author)