Bismayer, U.; Schmahl, Wolfgang W.; Schmidt, C.; Groat, L.A.
Linear birefringence and X-Ray diffraction studies of the structural phase transition in titanite, CaTiSiO5.
In: Physics and Chemistry of Minerals, Vol. 19, No. 4: pp. 260-266
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The antiferroelectric phase transition in titanite characterised by a collinear displacement of Ti-atoms from their central octahedral position is investigated using linear optical birefringence and X-ray diffraction techniques. Both methods indicate a continuous transition near 496 K and extra contributions to δΔn and X-ray intensity signals at higher temperatures. The critical exponent of the macroscopic order parameter is found to be β = 0.14 ± 0.02 and the transformation is interpreted in terms of a two-dimensional quasi-spin model. Topological features of the structure agree well with the spatial distribution of the diffuse scattering of the superstructure reflection 40 Mathematical expression.