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Diffuse phase transition in co doped barium titanate

1981; Taylor & Francis; Volume: 34; Issue: 1 Linguagem: Inglês

10.1080/00150198108238719

1563-5112

G. Godefroy, P. Chatry, L. Benguigui,

Ferroelectric and Piezoelectric Materials

Abstract Dielectric measurements were investigated in “fresh grown” Co substituted Barium Titanate crystals; the diffuse phase transition is analysed in two different models. The first one is a thermodynamic approach of the free energy with an apparent local field in the polarization direction: the best value for this field is calculated but the results do not fit very well the experimental data. The second one is based on a calculation of the polarization mean value under the assumption of a pseudo-gaussian distribution of the Co concentration. The dielectric constant is calculated in the classical Landau Devonshire formalism. The good fitting gives the values of the heterogeneity coefficient η in the different crystals.