This study investigates effects of the zinc oxide (ZnO) addition and the sintering temperature on the microstructure and the electrical properties (such as dielectric constant and loss tangent) of the lead-free piezoelectric ceramic of bismuth sodium titanate (Na0.5Bi0.5TiO3), NBT, which was prepared using the mixed oxide method. Three kinds of starting powders (such as Bi2O3, Na2CO3 and TiO2) were mixed and calcined. This calcined NBT powder and a certain weight percentage of ZnO were mixed and compressed into a green compact of NBT-ZnO. Then, this green compact of NBT-ZnO was sintered to be a disk doped with ZnO, and its characteristics were measured. In this study, the calcining temperature was 800 degrees C, the sintering temperatures ranged from 1000 to 1150 degrees C, and the weight percentages of ZnO doping included 0.0, 0.5, 1.0, and 2.0 wt%. At a fixed wt% ZnO, the grain size increases with increase in the sintering temperature. The largest relative density of the NBT disk obtained in this study is 98.3% at the calcining temperature of 800 degrees C, the sintering temperature of 1050 degrees C, and 0.5 wt% ZnO addition. Its corresponding dielectric constant and loss tangent are 216.55 and 0.133, respectively. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier BM. and The Society of Powder Technology Japan. All rights reserved.