Orthorhombic-to-Tetragonal Phase Transition in the Y-Ba-(Cu, Co)-O System

Abstract

X-ray powder diffraction, thermal analysis and resistivity measurements have been carried out for the YBa 2 (Cu 1- x , Co x ) 3 O 7-δ system with 0< x <0.333. With increasing Co content, weight loss in the thermogravimetric ( T G ) curve steadily decreases and the structure transforms from orthorhombic to tetragonal. Around this phase transition at x =0.02, T c starts to decrease. This phenomenon is considered to be ascribed to the disordering of oxygen sandwiched between Ba planes.