Phase Transitions

The Lattice Constant Vs. Temperature Relation Around The 105 K Transition Of A Flux-Grown Srtio3 Crystal

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In a flux-grown SrTiO3 crystal, monodomain and polydomain regions have been observed below the transition temperature without applying external stress. For each region, measurements of the lattice constant as a function of temperature are made by means of high-angle double-crystal X-ray diffractometry (HADOX) with a precision better than one part in 106The a(T) curve for the monodomain clearly shows a critical contraction in the region Tc ± 2 K, where the curve deviates from the relation 1 — a/a0 α (1 — T/Tc)ßa. The phenomenon is discussed in terms of the fluctuation of the order parameter and related to the precursor effect reported for KMnF3 and for SrTiO3 Verneuil crystals for T > Tc. This means, on the other hand, that the determination of the critical exponent of spontaneous strain of SrTiO3 is intrinsically difficult. An anomalous temperature dependence of the intensity of the 400 and 004 reflections found for Verneuil crystals is observed in a very similar manner. © 1985, Taylor & Francis Group, LLC. All rights reserved.


19 Aug 2006


Phase Transitions