[101]-Oriented (Li,Na,K) NbO3 ceramics prepared by magnetic field-assisted forming, sintering, and electric poling

Abstract

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 d33 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.