Phase-transition-like behaviour associated with the superconducting transition in Tl2Ca2Ba2Cu3Ox and BiSrCaCu2Ox compounds

A structural instability shown in the form of a phase-transition-like internal friction peak and step-like change of lattice parameters appears at 135 K in a Tl2Ca2Ba2Cu3Ox sample with zero resistance at 115 K. It was confirmed that the structural instability at 135 K coexisted with the superconducting transition at 115 K. In addition, a small internal friction peak and an ultrasonic attenuation peak, which may be related to the lower temperature superconductive phase, were observed at 90 K in the Tl-Ca-Ba-Cu-O material.