查看文章

The low-frequency mechanical properties of polycrystalline Ca_1−xSr_xTiO₃ (0.5 ≤ x ≤ 0.9) have been investigated as a function of temperature and bulk composition using the technique of dynamical mechanical analysis in three-point bend geometry. Ca_1−xSr_xTiO₃ forms a cubic solid solution at high temperatures. At lower temperatures it undergoes successive displacive transitions to tetragonal and orthorhombic phases on cooling and increasing CaTiO₃ content. The low-frequency mechanical response of the tetragonal phase is dominated by thermally activated displacements of transformation twin domain walls, causing almost a twofold decrease in storage modulus relative to the twin-free cubic phase on cooling through the phase transition (superelastic softening). Below 140 °C the mobility of domain walls decreases and the storage modulus returns to a value close to that of the cubic phase. For x > 0.85 …