2014 Le courant d'obscurité et la polarisation spontanée, obtenus en mesurant le courant pyroélectrique, ont été utilisés pour faire l'étude de la transition ferro-paraélectrique du SbSI. La valeur obtenue pour l'exposant critique de la polarisation spontanée est en accord avec la théorie du champ moyen (03B2 = 0,51 ± 0,02).

Measurements of pyroelectric current in needle shaped crystals of SbSexS1−xI (x ⪅ 0.01, x = 0.30, 0.33, 0.34, 0.38, 0.40, 0.50, 0.65) are carried out by measuring the potential difference across a short circuiting resistance while heating the samples at uniform rates. These measurements, together with dielectric constant show that the critical temperature (Tc) follows a rapid linear decrease when x increases up to 0.65 with a slope of 33 K per 0.1 of Se concentration. The spontaneous polarization deduced from measurement of the pyroelectric current seems consistent with a mean field theory. It is found that a critical point, where the order of the transition changes from first to second, occurs at a value of x around 0.30 ± 0.03. The fact that the spontaneous polarization does not go to zero at the critical temperature but rather decreases gradually when the temperature increases, for T > Tc may be attributed to composition fluctuations and internal stresses.

The pyroelectric effect is investigated in SbSe0.40S0.60I and the spontaneous polarization (Ps) and its derivative with respect to the temperature (λ) is deduced. The diffuse phase transition is analysed under the assumption of a non‐homogeneous composition through the sample. The good agreement between the theoretical predictions and experimental data allows the determination of the range where the selenium/sulfur ratio spreads.

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