Effect of Ge substitution on excess conductivity and infrared absorption of Tl_0·85Cr_0·15Sr_1−xGe_xCaCu₂O₇superconducting ceramics

Elastic moduli and step-like elastic anomalies in Ce-substituted Tl0.9Bi0.1Sr2−xCexCa0.9Y0.1Cu1.99Fe0.01O7−δ(x= 0–0.20) superconductors

“…[16À21] Tl 0.5 Pb 0.5 Sr 2¡y Mg y Ca 0.8 Yb 0.2 Cu 2 O 7¡d ceramic [17] was observed superconducting at temperature range of 98À103 K while Ge substitution in place of Sr site in Tl 0.85 Cr 0.15 Sr 2¡x Ge x CaCu 2 O 7¡d [16] superconducts at around 93À104 K. The changes in T c were attributed to reduction of average Cu valence from overdoped to optimally doped and underdoped states. Recent works involving substitution of higher valence ion of Ce 4C at Sr site of Tl 0.9 Bi 0.1 Sr 2¡x Ce x Ca 0.9 Y 0.1 Cu 1.99 Fe 0.01 O 7¡d ceramics have shown interesting results.…”