Variation of spontaneous strain of Y-Ba-Cu-O with temperature and oxygen stoichiometry

Abstract

Making combined use of X-ray diffraction data and thermogravimetry data at various temperatures and oxygen partial pressures, the spontaneous strain tensor for the ferroelastic superconductor YBa₂Cu₃O_7-x is computed (i) as a function of temperature for some fixed values of x, and (ii) as a function of x at a fixed temperature (room temperature). The observed anomalies are interpreted in terms of changes in vacancy ordering. It is suggested that monitoring of spontaneous strain, which is a kind of state parameter, can serve as a sensitive indicator of the departure from isotropy for this high-T_c superconductor.

Key Words:

• spontaneous strain
• ferroelastics
• superconductors
• Y-Ba-Cu-O
• vacancy ordering
• anisotropy