EFFECT OF A TWO-DIMENSIONAL PRESSURE ON THE CURIE POINT OF BARIUM TITANATE
MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INSULATION RESEARCH
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By hydraulics, a single crystal of BaTiO3 in the shape of a flat circular disk was subjected to a pressure exerted on the edges. After removal of all domains that were not normal to the disk by a slight pressure, the stress system consisted of equal pressures on the 2 a axes and none on the c axis. The transition temperature increased with the square of the 2-dimensional and hydrostatic stress systems was obtained by using Devonshires expansion for energy phil. Mag. 401040, 1949421065, 1951 and the appropriate Legendre transformation. The expansion had to be supplemented to obtain a quadratic effect. The evaluation of the effect of pressure on the transition temperature was difficult when higher terms were included, but the effect on Curie-Weiss temperature was easily determined. The laminar part of the Curie-Weiss temperature shift depended only on the lower terms in the free energy expansion it provided 2 independent relations for determining the 2 g coefficients. The quadraulic shift of the Curie-Weiss temperature depended on the higher terms with which the Devonshires exspansion was suupplemented, and an interpretation of these higher terms gave an upward direction to the shift.