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

In this paper, the effect of AgNbO3 on microstructure, dielectric and piezoelectric properties of [Li0.02(Na0.55K0.45)0.98][(Nb0.77Ta0.18Sb0.05)0.9976Cu0.006] (abbreviated as LNKNTSC) ceramics were investigated. AgNbO3 has attracted great interest due to the weak ferroelectric compound with a high Curie temperature (TC) of 360 degrees C. Lead-free (1-x)LNKNTSC-xAgNbO3 (x = 0 approximate to 0.075) piezoelectric ceramics were prepared by conventional solid solution method. All specimens were sintered in air at 1100 degrees C for 5hour. The density of LNKNTSC-AgNbO3 ceramics indicated a tendency to increase with increasing AgNbO3 content. The maximum density of 4.97g/cm3 was obtained at 7.5mol% AgNbO3 substituted ceramics. Therefore, AgNbO3 doping was sufficiently effective in promoting the densification of the ceramics. The piezoelectric constant d33 and planar electromechanical coefficient kp were increased with increasing AgNbO3 content. In addition, the tetragonal-orthorhombic phase transition temperature (TO-T) did not change largely as a function of AgNbO3 contents, which were approximately 140 degrees C. The density, electromechanical coupling factor (kp), mechanical quality factor (Qm) and piezoelectric constant (d33) of LNKNTSC ceramics with x = 0.075 showed the optimum values of 4.97g/cm3, 0.407, 138 and 205.33 pC/N, respectively.