STRUCTURAL INSTABILITY IN A Bi–Sr–Ca–Cu–O SYSTEM

Abstract

Measurements of internal friction and elastic modulus on Bi–Sr–Ca–Cu–O system reveal that a certain kind of phase transition take place a few tens degrees higher than T c . X-ray diffraction measurements show that the symmetry remains unchanged from room temperature to 77 K but the lattice parameters jump at the transition temperatures. Ferroelastic loop were measured around the temperatures mentioned above, which indicates the existence of movable boundaries and elastic softening. It is considered that the instability favor the superconducting transition followed.