Accession Number : AD0019933


Title :   EFFECT OF A TWO-DIMENSIONAL PRESSURE ON THE CURIE POINT OF BARIUM TITANATE


Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INSULATION RESEARCH


Personal Author(s) : Forsbergh, Jr, P W


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/019933.pdf


Report Date : Oct 1953


Pagination or Media Count : 23


Abstract : 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 Devonshire's expansion for energy (phil. Mag. 40:1040, 1949;42:1065, 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 Devonshire's exspansion was suupplemented, and an interpretation of these higher terms gave an upward direction to the shift.


Descriptors :   *CURIE TEMPERATURE , *BARIUM TITANATES , STRESSES , TRANSITION TEMPERATURE , SHIFTING , QUADRATIC EQUATIONS , FREE ENERGY , HYDROSTATICS , EXPANSION , DISKS , HYDRAULICS


Subject Categories : Thermodynamics


Distribution Statement : APPROVED FOR PUBLIC RELEASE