Electrical Properties and EPR Analyses of Mn-Doped 67PMN-33PT Piezoceramics

We conducted a study on Mn doping in 67Pb (Mg1/3Nb2/3)O3-33PbTiO3(67PMN-33PT), which is a ferroelectric material exhibiting a morphotropic phase boundary (MPB). The samples were doped with MnO2 at mass ratios ranging from 0.5 to 5.0wt.% and subsequently sintered at temperatures ranging from 1200 to 1260 degrees C. Experimental analysis of electrical properties was performed within the temperature range of -80-200 degrees C. Electron paramagnetic resonance (EPR) testing was conducted on these samples to investigate Mn solubility in PMN-PT ceramics and their existence in different valence states. The results indicate that at a doping ratio of 0.5wt.% and sintering temperature of 1220-1240 degrees C, Mn ions achieved a homogeneous dispersion within the crystal lattice, leading to the enhanced electromechanical Qm factor (510) and the reduced dielectric loss tan delta to minimum (0.30%) compared to the no doping Mn, however, as the Mn ions dopant content increase higher than 1.0wt.% and sintering temperatures 1200-1260 degrees, the unexpected results have been observed that both Qm and tan delta are enhanced to about 1200, 0.87 up to 1.5wt.% MnO2, and then, Qm decreases to 510, but tan delta increases to 3.78% for 5 wt.% MnO2. The machinal Qm and dielectric loss can be understood by the (Mn-Vo) defect dipoles in lattice, domain wall and grain-bounary, together with the increasing of the MnO2, Mn2O3 or their mixed phase of Mn3O4 in the grain boundary.