INFLUENCE OF THE LiNbO_3 AND KNbO_3 SEEDS ON THE SINTERING AND ELECTRICAL PROPERTIES OF PMN CERAMIC

摘要

The effect of LiNbO_3 and KNbO_3 seeds on the microstructure and dielectric characteristics of PMN ceramic prepared by columbite route have been investigated with the addition of 0, 1, and 2-wt percent of seeds. X-ray diffraction, Scanning Electron Microscopy and an impedance analyzer were used to characterize the influence of seeds on physical characteristics and dielectric properties of PMN. LiNbO_3-seeded PMN samples present a significant increase in the amount of perovskite phase. The addition of LiNbO_3 seeds in sintered PMN ceramics at 1100 deg C during 4 h causes a decrease in the porosity and the amount of pyrochlore phase. Weight losses during sintering of PMN ceramics are suppressed more significantly for LiNbO_3-seeded PMN. T_m of PMN ceramics changes with seeds concentration. KNbO_3 seeds displace T_m to lower temperature whereas LiNbO_3 causes its elevation, Dielectric constants of approximately 13,000 at 1 kHz was measured at -5 deg C in PMN ceramics with 1-wt percent of LiNbO_3 seeds.