Effect of Cd and Cd-Ca Substitution on the Superconductivity in Y1−xPrxBa2Cu3O7−δ Superconductor

The structural and superconducting properties of Y1−v−ηPrNCd{η}¨zCazBa2Cu3O7−δsystem are investigated using X-ray diffraction, ac susceptibility, dc resistivity, and oxygen content measurements. The effect of increasing Cd concentration substituting the Y-site in Y0.8Pr0.2Ba2Cu3O7-δ suppresses the superconducting transition temperature and lowers the hole concentration, unlike that of Ca substitution in Y0.8Pr0.2Ba2Cu3O7-δ which increasesTc due to hole doping by Ca. The suppression ofTc due to Cd substitution can be counterbalanced by simultaneous hole doping by Ca which increases the Tc with increasing Ca concentration. In spite of similarity in the ionic radii and valency, the role played by Cd and Ca substitution at the Y-site in the Y0.8Pr0.2Ba2Cu3O7-δ system is opposite in nature as Cd doping helps in Tc suppression due to the Pr effect, suggesting that Cd does not provide the necessary holes like Ca substitution which helps to increase the Tc by the hole doping mechanism.