Structure and superconducting properties of the Tl1 –δ CaBa2Cu2O7 and Tl1 –δY1 –xCaxBa2Cu2O7 series

Abstract

Superconducting Tl_{1 –δ}CaBa₂Cu₂O₇ can be prepared without impurity from the corresponding two Tl–O layer cuprate only when some Tl deficiency is incorporated. The Tl_{1 –δ}CaBa₂Cu₂O₇ and Tl_{1 –δ}Y_{1 –x}Ca_xBa₂Cu₂O₇ series show maximum T_c at an optimal hole concentration. The T_c maximum occurs at a Cu—O distance of ca. 1.924 Å.