Field-induced relaxation of crystal structure in dipole-glass phase of PMN — PT single crystal: X-ray study

Abstract

X-ray studies of the electric field-induced structural changes in 0.8PMN — 0.2PT single crystal were made in the temperature range 300–400 K including the points of the supposed dipole-glass (T _DG ≈ 352 K) and ferroelectric (T _F ≈ 324) transitions. The changes in the form and intensities of the 005 and 224 reflexes were studied after the application the different electric fields (E < 5 × 10⁵ V/m) along [001] cubic direction. At T > T _DG and T < T _F the instantaneous changes in the form and the intensity of the 224 reflex are in accordance with the cubic and rhombohedral symmetries of the parent and ferroelectric phases correspondingly, while at T _F < T < T _DG the field above some (temperature dependent) threshold value induces the smearing of this Bragg peak followed by the slow (during 30–40 min.) formation of the broad multiplet structure.

Also the influence of the slow ac field (frequency 0.01 Hz) on the averaged over the period Bragg peak form was studied at 300 K < T < 400 K.

Key Words:

• Phase transitions
• X-ray diffraction
• dipole-glass
• ferroelectric
• spontaneous atomic shifts