In-situ X-ray diffraction study of ferroelectric domain switching in orthorhombic NKN ceramics

The family of perovskite ferroelectrics based on sodium potassium niobate (NKN) ceramics exhibit useful piezoelectric properties and show potential for the replacement of conventional lead based piezoceramics. In the present study, iron-doped NKN ceramics were prepared by a solid state reaction method. Ferroelectric hysteresis measurements indicated that a remanent polarization value approaching 0.4Cm-2 could be obtained by poling under a continuous AC electric field with amplitude of 3 MV m-1. X-ray diffraction (XRD) patterns of these materials were recorded in transmission during poling, using high energy synchrotron X-rays with a wavelength of 1.55 × 10-11m. Changes in crystallographic texture were observed during poling as a result of 90° and 60°/120° domain switching. The strain due to ferroelectric domain switching in orthorhombic NKN is described in terms of the differences in transformation strain between different domain variants, with reference to the high temperature cubic lattice.