Ferroelectricity

Effect of electric field on the smeared phase transition in crystals PbIn$_{1/2}$Nb$_{1/2}$O$_3$–28PbTiO$_3$ and PbIn$_{1/2}$Nb$_{1/2}$O$_3$–37PbTiO$_3$

L. S. Kamzina, S. N. Popov

Ioffe Institute, St. Petersburg

Abstract: The effect of a direct-current electric field (0 $<E\le$ 3 kV/cm) on the smearing of the phase transition and the Curie–Weiss exponent $(\gamma)$ for two PbIn$_{1/2}$Nb$_{1/2}$O$_3$–28PbTiO$_3$ and PbIn$_{1/2}$Nb$_{1/2}$O$_3$–37PbTiO$_3$ crystals lying at different distances from the morphotropic phase boundary has been investigated. The universal Curie–Weiss law has been used to approximate the temperature dependences of the dielectric permittivity. It has been shown that the more remote is the crystal from the morphotropic phase boundary, the larger is the exponent $\gamma$ and, consequently, the more smeared is the phase transition (in the zero field, $\gamma$ = 1.67 and 1.49 for PbIn$_{1/2}$Nb$_{1/2}$O$_3$–28PbTiO$_3$ and PbIn$_{1/2}$Nb$_{1/2}$O$_3$–37PbTiO$_3$, respectively). It has been found that a weak electric field (no greater than 2–3 kV/cm) in the case of the more smeared phase transition almost does not affect the Curie–Weiss exponent, whereas for the PbIn$_{1/2}$Nb$_{1/2}$O$_3$–37PbTiO$_3$ crystal, this exponent decreases with increasing electric field strength and approaches $\gamma$ = 1, which is characteristic of the conventional ferroelectric.

Received: 14.04.2014
Accepted: 02.06.2014

 English version: Physics of the Solid State, 2014, 56:11, 2213–2216

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