[101]-Oriented (Li,Na,K) NbO 3 ceramics prepared by magnetic field-assisted forming, sintering, and electric poling

Crystal orientation is a strategy for the improvement of piezoelectric properties of lead-free piezoelectric materials. [101]-Oriented Li-modified (Na,K) NbO3 ceramics (LNKN) were fabricated using a colloidal method under a strong magnetic field, sintering, and subsequent electrical poling. For the Li0.06Na0.52K0.42NbO3 powder compact, which has a monoclinic phase at room temperature, the (-101) planes were oriented perpendicular to the magnetic field. Although the monoclinic phase transitioned to tetragonal and cubic phases above the Curie temperature during sintering, the crystal-oriented structure was maintained and developed even after phase transitions and grain growth during sintering. Furthermore, crystal reorientation was enhanced by domain switching under an electric field. Thus, [101]-oriented LNKN ceramics with a tetragonal crystal system were obtained. The piezoelectric d(33) constant was improved to 208 pC/N from 112 pC/N due to the effects of electromechanical coupling coefficient and specific dielectric coefficient by the texturing process with magnetic field assisted shaping, sintering, and electrical poling. (C) 2019 The Ceramic Society of Japan. All rights reserved.