Effects of Alkali Metal Content and Sintering Temperature on the Structure and Electrical Properties of (Na0.52K0.48) 0.94+xLi0.06-xNb0.94Sb0.06O3 Lead-Free Piezoelectric Ceramics

Alkali niobate lead-free piezoelectric ceramics with nominal compositions [(Na0.52K0.48)0.94+ xLi0.06-x](Nb0.94Sb0.06)O3 ((NK)xLNS) were prepared by normal sintering. Crystalline phase, piezoelectric properties and sintering behavior of (NK)xLNS ceramics were investigated with a special emphasis on the influence of alkli metal content. The x-ray diffraction patterns and the corresponding calculation of lattice parameters indicated that a phase transition from tetragonal to orthorhombic symmetry occurs as x=0.01, resulting in enhanced piezoelectric constant and planar electromechanical coupling coefficient of 266 pC/N and 38.5%, respectively. With x=0.01, the ceramics sintered at 1050 C show higher density and better electrical properties. Our results indicate the importance of sintering temperature and elaborate compositional control for enhancing piezoelectric properties in niobate-based ceramics.