Effect of transformation twins on the anelastic behavior of polycrystalline Ca1−xSrxTiO3 and SrxBa1−xSnO3 perovskite in relation to the seismic properties of Earth's mantle perovskite

The mechanical loss of Ca1−xSrxTiO3 as a function of temperature has been studied up to 1000 °C using dynamical mechanical analysis. The loss spectrum reveals a relaxation peak in the tetragonal phase and negligible mechanical loss in the cubic and orthorhombic phases. The peak is accompanied by a softening of the storage modulus, caused by the formation of mobile transformation twin domain walls. The small value of internal friction in the orthorhombic phase is associated with a negative volume strain, resulting in domain walls that are strongly pinned by lattice defects. The volume changes and mechanical loss in Ca1−xSrxTiO3 are compared with those in SrxBa1−xSnO3, a system which shows a positive volume strain. In contrast to Ca1−xSrxTiO3, SrxBa1−xSnO3 displays a thermally activated peak in the orthorhombic phase. A frequency-independent peak attributed to the tetragonal–orthorhombic transition is also seen. The positive volume strain in SrxBa1−xSnO3 results in domain wall structures that are less strongly pinned by lattice defects.