Piezoelectric K0.5Na0.5NbO3 Ceramics Textured Using Needlelike K0.5Na0.5NbO3 Templates

Abstract

Improved performance by texturing has become attractive in the field of lead-free ferroelectrics, but the effect depends heavily on the degree of texture, type of preferred orientation, and whether the material is a rotator or extender ferroelectric. Here we report on successful texturing of K0.5Na0.5NbO3 (KNN) ceramics by alignment of needle-like KNN templates in a matrix of KNN powder using tape casting. Homotemplated grain growth of the needles was confirmed during sintering, resulting in a high degree of texture parallel to the tape casting direction and the aligned needles. The texture significantly improved the piezoelectric response parallel to the tape cast direction, corresponding to the direction of the strongest pc orientation, while the response normal to the tape cast plane was lower than for a non-textured KNN. In situ X-ray diffraction during electric field application revealed that non-180° domain reorientation was enhanced by an order of magnitude in the tape casting direction, compared to the direction normal to the tape cast plane and in the non-textured ceramic. The effect of texture in KNN is discussed with respect to possible rotator ferroelectric properties of KNN.