Effect of rare earth additives on the microstructure and dielectric properties of 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 ceramics

Microstructure and dielectric properties of relaxor ferroelectrics in the solid solution, formulated 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 + 2 mol% RE (RE = Sm, Nd, Yb or Ce), have been investigated. The effects of these dopants on microstructure, maximum dielectric constant (Kmax) and degree of ordering, etc. have been studied. It was found that doping of Sm, Nd and Ce reduced Kmax from 23924 to 14921, 13466 and 12511 respectively, while the doping of Yb increased Kmax to 27759. The variation of Kmax is analyzed according to grain size, domain structure and order-disorder behavior. Diffuseness of the phase transition is calculated to indicate order-disorder behavior, which is roughly opposite to that of Kmax. The present results show that order-disorder behavior is the key factor on Kmax of PMN-PT ceramics near morphotropic phase boundary.