Lead magnesium niobate relaxor ferroelectric ceramics of low-firing for multilayer capacitors

Lead-magnesium-niobate relaxor ferroelectric ceramics with a high dielectric constant and low sintering temperature for multilayer capacitors have been studied. PMN-PT-PCW and PMN-PT+excess PbO+excess MgO with normal, chemically pure raw materials processed by the direct formation of oxides (mixed-oxides procedure) were sintered at 860-960 degrees C. Values of epsilon max from 13000 to 18500 (at 1 kHz) and good aging characteristics were obtained. By means of X-ray diffraction analysis, it was found that the amount of pyrochlore phase is less than 2-3% in both the calcined powder and the samples. The dielectric constant of PMN-based ceramics was found to increase with excess MgO and excess PbO. A dense uniform microstructure was obtained at low firing temperatures. The selected-area diffraction pattern shows a ratio of niobium to magnesium of 1:1.<
>