Electrical properties and chemical characterization of PMN and 0.90 PMN-0.10PT

The relationships between the synthesis and processing, atomic-level and long-range structure, and the electrical properties of lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃ (PMN), and the solid solution systems with lead titanate, PbTiO₃ (PT), have been investigated. High-purity PMN and 0.90PMN-0.10PT powders were synthesized using the columbite, modified columbite, mixed oxide and molten salt methods. X-ray diffraction analysis of the powders and pressed ceramics show phase purity variations from 70-100% PMN perovskite. Solid-state ⁹³Nb MAS NMR spectra of PMN powders and ceramics from the molten salt and modified columbite show differences in the ⁹³Nb resonances due to ordered and disordered regions in the PMN. Broadband electrical properties measurements, including unbiased and dc field-induced dielectric properties from -40 to 180°C, and the electric field dependence of strain and polarization were measured for selected PMN ceramics. The dielectric measurements measured at 1 kHz yielded a K_max of 20,000 for the molten salt PMN (at -8°C) and 17,900 for the columbite PMN (at -4°C). The molten salt 0.90PMN-0.10PT exhibited a K_max of 26,000 at 1 kHz. Piezoelectric coupling factors of approximately 0.50 were measured for the 0.90PMN-0.10PT from the molten salt synthesis, with a dc bias of 0-15 kV/cm. SEM analysis of PMN ceramics obtained by the molten salt and columbite methods of powder synthesis show differences in both grain size distribution and heterogeneity