PROCESSING, SINTERING CHARACTERISTICS AND DIELECTRIC-PROPERTIES OF BARIUM-SUBSTITUTED PB(MG1 3NB2/3)O-3-PBTIO3 SOLID-SOLUTION/

Solid solutions in the lead-based relaxer system Pb(Mg1/3Nb2/3)O-3-PbT iO3 were modified by minor substitutions of Ba in the Pb-site of the p erovskite lattice. The modified compositions were calcined at 830 degr ees C for 3 h to yield fine-grained, single-phase perovskite materials . A small amount of excess MgO(0.05 wt %), which mostly served as a si ntering aid, was added to the calcined batches and the resulting mixtu res were sintered at temperatures between 1150 and 1250 degrees C for periods ranging from 3 to 5 h. The substitutions of BaO for PbO in the perovskite solid solution lattice caused a progressive lowering of th e Curie point with increasing BaO content. On average, the Cu rie poin t decreased by about 10 degrees C for each mole of BaO substituted for PbO. Among the various Ba-substituted solid solutions studied, the on e with a nominal composition Pb0.99Ba0.01[(Mg1/3Nb2/3)(0.9)Ti-0.1]O-3, which has a Curie point located near 28 degrees C, exhibited excellen t dielectric properties. On sintering at 1250 degrees C for 3 h, this composition yielded a density near 96% of the theoretical density. The peak dielectric constant of the composition at 1 KHz was slightly hig her than 22 000, and the corresponding tan delta value was 1.5% with a specific resistivity of 2.5 x 10(12) Ohm cm(-1).