DENSIFICATION BEHAVIORS AND PIEZOELECTRIC PROPERTIES OF MNO2, SIO2-DOPED PB(NI1 3NB2/3)O3-PBTIO3-PBZRO3 CERAMICS/

The roles of additives (MnO2, SiO2, and CdO) in controlling microstruc tural development and piezoelectric properties of Pb(Ni1/3Nb2/3)O3-PbT iO3-PbZrO3(PNN-PT-PZ) ceramics were systematically examined. The addit ion of SiO2 (<1 wt.%) to the pseudoternary PNN-PT-PZ system enhances d ensification, but suppresses grain growth significantly. On the other hand, the presence of MnO2 expedites the rate of grain growth without increasing the rate of densification appreciably. The observed differe nce in the grain-growth behavior was discussed in terms of the viscosi ty of liquid phase formed during sintering and the diffusion-controlle d process for the solute-atoms transport. The rapid increase in the me chanical quality factor (Q(m)) and the decrease in the relative dielec tric permittivity (epsilon(r)) and d33 for the MnO2-doped specimens in dicate the formation of oxygen vacancies by the dissolution of Mn-atom s into the B-sites of perovskite structure. On the contrary, the prese nce of CdO (2 mol %) remarkably increases epsilon(r) and d33 of PNN-PT -PZ ceramics.