(Na0.5K0.5)NbO3–LiTaO3 lead-free piezoelectric ceramics

• Published in: Materials letters Vol. 59; no. 2-3; pp. 241 - 244
• Main Authors: Guo, Y, Kakimoto, K, Ohsato, H
• Format: Journal Article
• Language: English
• Published: 01-01-2005
• ISSN: 0167-577X
• DOI: 10.1016/j.matlet.2004.07.057

Lead-free piezoelectric ceramics were prepared in the system (1-x)(Na0.5K0.5)NbO3-xLiTaO3 following the conventional mixed oxide route. The effect of cationic substitution of lithium for sodium and potassium in the A sites and tantalum for niobium in the B sites in (Na0.5K0.5)NbO3 (NKN) perovskite lattice on symmetry and physical properties were investigated. The materials with perovskite structure are in orthorhombic phase when x < 5 mol% and transform to tetragonal phase when x > 6 mol%; when x is at least 8 mol%, a K3Li2Nb5O15 phase with tetragonal tungsten bronze structure begins to appear and becomes dominant with increasing content of LiTaO3. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases appears at x = 5-6 mol%. Analogous to Pb(Zr,Ti)O3, the piezoelectric and electromechanical properties are enhanced for compositions near the morphotropic phase boundary. Piezoelectric constant d33 values reach about 200 pC/N. Electromechanical coefficients of planar mode reach about 36%, respectively. Results show that (Na0.5K0.5)NbO3 with small amounts of LiTaO3 (x less than or equal to 7 mol%) is a good lead-free piezoelectric ceramic. 14 refs.