Structure and electrical properties of K0.5Na0.5NbO3–LiSbO3 lead-free piezoelectric ceramics

Abstract

Lead-free piezoelectric ceramics ͑1−x͒K 0.5 Na 0.5 NbO 3 -xLiSbO 3 have been fabricated by a conventional ceramic sintering technique. The results of x-ray diffraction suggest that Li + and Sb 5+ diffuse into the K 0.5 Na 0.5 NbO 3 lattices to form a solid solution with a perovskite structure. The ceramics can be well sintered at 1070-1110°C. The introduction of LiSbO 3 into the Na 0.5 K 0.5 NbO 3 solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature ͑T c ͒, but greatly shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition ͑T O-F ͒ to room temperature. Coexistence of the orthorhombic and tetragonal phases is formed at 0.05Ͻ x Ͻ 0.07 at room temperature, leading to a significant enhancement of the piezoelectric properties. For the ceramic with x = 0.06, the piezoelectric properties become optimum: piezoelectric constant d 33 = 212 pC/ N, planar and thickness electromechanical coupling factors k P = 46% and k t = 47%, respectively, remanent polarization P r = 15.0 C/cm 2 , coercive field E c = 1.74 kV/ mm, and Curie temperature T C = 358°C.

Piezoelectric properties of (Li, Ag, Sb) modified (K0.50Na0.50)NbO3 lead-free ceramics

“…So a MPB between orthorhombic and tetragonal ferroelectric phases of the (1 − x)KNNL-xAS ceramics was identified in the composition range of 0.01 < x < 0.03. The electrical characterization was focused only on these compositions around the MPB [6,8,9], which will be discussed later. Fig.…”

“…The morphotropic phase boundary (MPB) of the materials is an important factor to affect the electrical properties [6,8,9]. The high piezoelectric response was generally considered to * Corresponding author.…”

“…be obtained from the MPB between rhombohedral, tetragonal, and/or monoclinic ferroelectric phases. Therefore, currently the main research activities in this area are to search for new leadfree compositions with MPB by means of a huge amount of experimental work [6,8,9].…”

“…Therefore, it is necessary to search for lead-free piezoelectric ceramics with excellent properties. Recently, much attention for lead-free piezoelectric ceramics has been paid to (K 0.5 Na 0.5 )NbO 3 (KNN)-based ceramics because of its environmental harmony, good electrical properties, and high Curie temperature [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Lead-Free Piezoelectric Transducers for Microelectronic Wirebonding Applications

“…However, because of the high volatility of alkaline elements at high temperatures, it is very difficult to obtain dense and well-sintered KNN ceramics using a conventional sintering process, and the ceramics usually exhibit worse piezoelectric properties (d 33 = 80 pC/N, k p = 0.36) and low density (= 4.25 g/cm 3 ). A number of studies have been carried out to improve the sinterability and properties of KNN ceramics; these include the formation of solid solutions of KNN with other ABO 3 -type ferroelectrics or nonferroelectrics, e.g., LiNbO 3 (Guo et al, 2004), Bi 0.5 Na 0.5 TiO 3 (Zuo et al, 2007), BaTiO 3 (Ahn et al, 2005), Ba(Ti 0.95 Zr 0.05 )O 3 (Lin et al, 2007a), SrTiO 3 (Wang et al, 2005), LiTaO 3 (Guo et al, 2005), and LiSbO 3 (Lin et al, 2007b), the substitutions of analogous ions (e.g., Li + , Sb 5+ and Ta 5+ ) for the A-site K + and Na + or the B-site Nb 5+ ions (Saito et al, 2004;Lin et al, 2008a), and the use of sintering aids, e.g., CuO (Lin et al, 2008b) and K 5.4 Cu 1.3 Ta 10 O 29 (Matsubara et al, 2005). Among various KNN-based ceramics, KNN ceramics co-modified with Li and Ta have been widely studied, and good piezoelectric properties have been reported for several compositions, e.g., (K 0.5 (Saito et al, 2004 Lee, 2008).…”