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The postdoctoral report has been divided into two parts. In the first section, the compositional and firing properties of Pb(Zn1/3Nb2/3)0.20(Zr0.50Ti0.50)0.80O3 system(0.2PZN-0.8PZT) doped with different additives, i.e. Cr2O3, MnO2 and CuO, have been studied as well as its dielectric and piezoelectric properties. The second section describes the synthesis of two novel ABO3 type ceramics, i.e. ZnTiO3 and K0.5Bi0.5TiO3 (KBT), by sol-gel technique, and their thermal behavior and electric properties have also been investigated in detail.
Cr2O3 doped 0.2PZN-0.8PZT ceramics with pure perovskite structure were fabricated by the columbite precursor method. Addition of Cr2O3 stabilized the tetragonal phase against the rhombohedral one, moving morphotropic phase boundary(MPB) composition toward the PbZrO3-rich side. The grain size was steadily enhanced when small amounts of Cr2O3 were added to system. Addition of Cr2O3above the solubility of 0.3wt％ inhibited the grain growth due to accumulation of Cr ion at the grain boundary. The values of electromechanical coupling factor, kp,piezoelectric constant, d33 are optimized for 0.3wt％ Cr2O3 doped samples (kp=0.70,d33=491 pC/N), which suggested that the effects of grain size plays a dominant role on improving the piezoelectric properties than that of oxygen vancancies in the low Cr2O3 doping region of 0 to 0.3wt％. However, the value of mechanical quality factor,Qm is only 140 at 0.3wt％ Cr2O3, which limits their application in resonators or transformers.