Effects of AgNbO₃ on Microstructure, Dielectric and Piezoelectric Properties of (Li,Na,K) (Nb,Ta,Sb,Cu)O₃ System Ceramics

Abstract

In this paper, the effect of AgNbO₃ on microstructure, dielectric and piezoelectric properties of [Li_0.02(Na_0.55K_0.45)_0.98][(Nb_0.77Ta_0.18Sb_0.05)_0.9976Cu_0.006] (abbreviated as LNKNTSC) ceramics were investigated. AgNbO₃ has attracted great interest due to the weak ferroelectric compound with a high Curie temperature (T_C) of 360°C. Lead-free (1-x)LNKNTSC-xAgNbO₃ (x = 0 ∼ 0.075) piezoelectric ceramics were prepared by conventional solid solution method. All specimens were sintered in air at 1100°C for 5 hour. The density of LNKNTSC-AgNbO₃ ceramics indicated a tendency to increase with increasing AgNbO₃ content. The maximum density of 4.97 g/cm³ was obtained at 7.5 mol% AgNbO₃ substituted ceramics. Therefore, AgNbO₃ doping was sufficiently effective in promoting the densification of the ceramics. The piezoelectric constant d₃₃ and planar electromechanical coefficient k_p were increased with increasing AgNbO₃ content. In addition, the tetragonal-orthorhombic phase transition temperature (T_O-T) did not change largely as a function of AgNbO₃ contents, which were approximately 140°C. The density, electromechanical coupling factor (k_p), mechanical quality factor (Q_m) and piezoelectric constant (d₃₃) of LNKNTSC ceramics with x = 0.075 showed the optimum values of 4.97 g/cm³, 0.407, 138 and 205.33 pC/N, respectively.

Keywords:

• Piezoelectric
• Lead-free Ceramic
• AgNbO₃
• Piezoelectric Coefficient

Acknowledgments

This work was supported by the Power Generation & Electricity Delivery of the Korea Insitute of Energy Technology Evaluation and planning(KETEP) grant funded by the Korea government Ministry of Knowledge Economy. (No. 2010T100100282)