Elastic constants and Debye temperature of polycrystalline Y₁Ba₂Cu₃O_7−x

Using ultrasonic methods, the quasi-isotropic elastic stiffnesses of void-containing Y₁Ba₂Cu₃O_7−x were determined By a composite-material model, these were corrected to the void-free state. From these, the Debye characteristic temperature was calculated. All the elastic stiffnesses fall well below those of polycrystalline BaTiO₃, an approximate crystalstructural building block of Y₁Ba₂Cu₃O_7−x. The low apparent stiffness may result from oxygen vacancies, which soften interionic forces. Also, it may result from microcracks, which reduce elastic stiffness without lowering mass density.