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

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 442; no. 1-2; pp. 199 - 203
• Main Authors: DARAKTCHIEV, M, HARRISON, R. J, MOUNTSTEVENS, E. H, REDFERN, S. A. T
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Amsterdam Elsevier 20.12.2006
• Subjects: Anelasticity, internal friction, stress relaxation, and mechanical resonances; Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Mechanical and acoustical properties of condensed matter; Physics; Solid-solid transitions; Specific phase transitions; Crystal twin; Cubic lattices; Ferroelastic transformation; Crystal defects; Internal friction; Stannates; Phase transformations; Ferroelastic phase transitions; Elastic softening; Polycrystals; Titanates; Domain wall motion; Perovskites; Negative/positive volume strain; Domain wall thickness; Domain structure; Orthorhombic lattices; Anelasticity; Mechanical loss; Wall pinning; Activation energy
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2006.01.141

The mechanical loss of Ca1-xSrxTiO3 as a function of temperature has been studied up to 1000 deg 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.