EFFECT OF EXCESS MgO ON DIELECTRIC PROPERTIES OF PMN-PT CERAMICS WITH ZnO ADDITIVE

PMN-PT ceramics with ZnO additive were prepared by the columbite precursor method and their microstructure and dielectric properties were investigated as a function of excess MgO content. The PMN-PT ceramics with pure perovskite phase and relative density cif 95% were obtained at 1150 degrees C by the addition of 2 mol% ZnO. For the 2 mol% ZnO-added PMN-PT, the addition of excess MgO up to 2 mol% led to increases in grain size, dielectric constant and electrostrictive strain. Further addition of excess MgO degraded these values, mainly due to the inhibited grain growth resulting from the precipitation of an Mg-rich phase. For the no-ZnO-added specimen, the grain size and dielectric properties increased with increasing excess MgO up to 5 mol% and then decreased with further excess MgO addition.