In this study non-stoichiometric (K0.5Na0.5)0.97(Nb0.96-xTaxSb0.04)O3 ceramics were prepared by the conventional soild-state teaction method. The effect of Ta-substitution on the dielectric and piezoelectric properties were investigated. X-ray diffraction analysis of all the specimens less than x= 15 mol% indicated orthorhombic phase. Thereafter, the specimens showed orthorhombic phase near to pseudo-cubic. Sinterablity of all the specimens was improved due to secondary products such as KCT and KCN. The ceramics with x= 5 mol% showed the optimum velues of pizoelectric constant(d33)= 150 pC/N, electromechanical coupling factor (kp)= 0.45, electromechanical quality factor (Qm)= 418.9 and dielectric constant(εr)= 567. Accordingly, These results indicate that the composition ceramics is a promising candidate for lead-free material.

We investigated the physical properties of stoichiometric and non-stoichiometric oxide doped complex perovskite, Ba(Zn1/3Ta2/3)O3 ceramics and their impacts on the microwave dielectric performances using various characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and network analyzer. According to the measurement of lattice constant changes, anomalous lattice volume contraction of ZrO2 doped Ba(Zn1/3Ta2/3)O3 sample only showed the dielectric quality factor enhancements, which was due to the lattice volume contraction as well as the 1:2 B-site cation ordering. In addition, NiO doping was useful to the stabilization of temperature coefficient of resonance frequency.

In this study, non-stoichiometric 1-x[(K0.5Na0.5)0.97(Nb0.96Sb0.04)O3] + x CeMnO3 + 0.8 mol%CuO + 0.2 wt% Ag2O (x=0, 0.005) ceramics were prepared by a conventional mixed oxide and carbonate method, their dielectric and piezoelectric properties were investigated with the variations of sintering temperature. As CeMnO3 substitution incereased, the density, piezoelectric constant(d33) and dielectric constant(εr) were increased and the mechanical quality factor(Qm) was decreased. At the sintering temperature of 1100℃, the density, electromechanical coupling factor(kp), dielectric constant(εr) and piezoelectric constant(d33) of 0.5mol% CeMnO3 specimen showed the optimun values of 4.475 g/㎤, 0.437, 552 and 166 pC/N, respectively. However, the mechanical quality factor(Qm) showed the minimum value of 380.