Study of domain structure of poled (K,Na)NbO3 ceramics

Abstract

Domain structure may greatly affect the dielectric and piezoelectric properties of a ferroelectric ceramic material. However, no investigations on the domain structure of poled (K,Na)NbO3-based ceramics have been reported so far. Since (K0.50Na0.50)NbO3 is the basic composition for the important type of lead-free piezoelectric materials, domain structure of the poled (K0.50Na0.50)NbO3 ceramics with the average grain size of about 8 μm were explored by observing the domain patterns with an acid etching technique in this study. It was found that domain patterns show usually either a single set of parallel domain stripes or a few sets of parallel domain stripes in polycrystalline grains. The average domain widths in different sets of parallel domain stripes vary largely from 150 nm to 750 nm. The intersection angels between two adjacent sets of domain stripes are around 45° or 135°. Two models of domain configuration were proposed to explain those domain patterns that consist of more than two sets of parallel domain stripes. One is built up in the way that the intersection angles between two adjacent sets of domain stripes are acute and consists of 90°-, 60°- and 120°-domain walls. The other one is formed in the way that the intersection angles between two adjacent sets of domain stripes are obtuse and is composed of 180°-, 90°- and 120°-domain walls. Additionally, the change of intersection angle between two adjacent sets of domain stripes with varying the observation plane is discussed.