Piezoelectric Properties and Local Structure Analysis of (1-<i>x</i>)(Na_0.50K_0.45Li_0.05)NbO₃-<i>x</i>(Ba_0.85Ca_0.15)(Zr_0.10Ti_0.90)O₃ Solid Solutions Produced by Malic Acid Complex Solution Method

Abstract

((1-x)(Na 0.50 K 0.45 Li 0.05 )NbO 3 x(Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O 3 (NKLNBCZT, x = 00.08) powders were synthesized by the malic acid complex solution method, and NKLNBCZT solid solutions were then fabricated using a conventional solid-state reaction technique. The piezoelectric properties of the resulting materials were measured, and the x = 0.01 sample was found to exhibit the maximum longitudinal-length-mode piezoelectric coefficient and radial-mode electromechanical coupling factor values of 177 pC/N and 33, respectively. On the basis of both the results for piezoelectric properties and for the local structural analysis using high-energy X-ray diffraction (HEXRD), measuring the degree of distortion of NbO 6 octahedra using HEXRD can be an effective method for the development of high-performance piezoelectric materials.Key words: lead-free piezoelectric, alkali niobate, NKLNBCZT, local structure analysis INTRODUCTIONPiezoelectric ceramics are widely used in communications devices, electrical appliances, medical devices and aerospace applications. In terms of its performance and operating temperature range, lead zirconium titanate, Pb(Zr,Ti)O 3 (PZT), offers many advantages due to its excellent piezoelectric properties (longitudinal-length-mode piezoelectric coefficient d 33 = 300374 pC/N and radial-mode electromechanical coupling factor k p = 5865%) and its comparatively high Curie temperature (T c = 260365C) [1,2]. However, because of global environmental concerns, there has recently been a large amount of research into developing high-performance lead-free alternatives to PZT [3].One highly promising lead-free material is sodium potassium niobate, (Na,K)NbO 3 (NKN), which also exhibits excellent piezoelectric properties and a high T c of 410C [4,5]. In 2004, Guo et al. reported that (Na,K,Li)NbO 3 , which is produced by isovalent replacement of Li ions at the A-sites in the NKN perovskite structure, exhibited excellent piezoelectric properties and a high T c of more than 450C [6]. Moreover, Nakai et al. who were members of our research group, revealed that (Na 0.50 K 0.45 Li 0.05 )NbO 3 (NKLN) solid solutions produced by the malic acid complex solution method (MACSM) were soft materials exhibiting excellent piezoelectric properties, with a d 33 of 151 pC/N, a k p of 32% and a radial-mode mechanical quality factor Q m (p) of 87, and a high T c of 462C [7]. Meanwhile Ba(Zr 0.2 Ti 0.8 )O 3 x(Ba 0.7 Ca 0.3 )TiO 3 (BZTxBCT) solid solutions with the same crystal structure as NKLN have attracted much attention due to their good piezoelectric properties at the tricritical point of the morphotropic phase boundary (MPB) between the rhombohedral (R) and