Abstract
The mechanical loss of Ca 1− x Sr x TiO 3 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 Ca 1− x Sr x TiO 3 are compared with those in Sr x Ba 1− x SnO 3, a system which shows a positive volume strain. In contrast to Ca 1− x Sr x TiO 3, Sr x Ba 1− x SnO 3 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 Sr x Ba 1− x SnO 3 results in domain wall structures that are less strongly pinned by lattice defects.
Published Version
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