Evolution of the ferroelectric phase in 〈001〉-oriented (100 − x)PbMg1/3Nb2/3O3-xPbTiO3 single crystals

Abstract

The effect of a dc electric field on the nucleation and evolution of the phase with long-range order in a cubic nonpolar matrix in 〈001〉-oriented (100 − x)PbMg1/3Nb2/3O3-xPbTiO3 single-crystal relaxors as the content of PbTiO3 is gradually increased (6 ≤ x ≤ 20, where x is the PbTiO3 content given in molecular percent) is investigated. The optical properties of these solid solutions are studied in different modes of application of an electric field. It is shown that an applied electric field with a strength above a threshold value induces a first-order ferroelectric phase transition with a temperature hysteresis occurring between measurements performed under cooling and heating of the crystal in the electric field. As the PbTiO3 content or electric field strength increases, the hysteresis becomes less pronounced and the first-order phase transition is suppressed. At x ∼ 20, the induced transition resembles a second-order rather than first-order transformation. It is assumed that, for compositions with x > 10 in electric fields higher than 4 kV/cm, the formation of the rhombohedral phase is accompanied by the appearance of another (possibly, monoclinic) phase associated with the rotation of the polarization vector from the [111] direction of the rhombohedral phase to the [001] direction of the tetragonal phase.