MULTILAYER CAPACITOR CERAMICS IN THE PMN-PT-BT SYSTEM - EFFECT OF MGOAND 4PBO-CENTER-DOT-B2O3 ADDITIONS

Coexistence of pyrochlore phase is one of the major problems in the pr eparation of lead magnesium niobate (PMN) based perovskites as it lead s to deterioration of the dielectric and piezoelectric properties. Alt hough the columbite precursor method substantially reduces the formati on of pyrochlore phase, the success of this process depends on various process conditions such as reactivity of MgO, level of mixing or grin ding, control of PbO volatility and reversibility of the reaction. Com positions in the system (1 - x)[(1 - y)PMN yPT]xBT (where PT = PbTiO3 and BT = BaTiO3) were prepared by the columbite route. Results show th at addition of excess MgO and 4PbO . B2O3 glass before sintering not o nly eliminates the pyrochlore phase completely but also produces a ser ies of ceramics with low firing temperature, very high dielectric cons tant, low dissipation factor, high d.c. resistivity and extremely low temperature coefficient of capacitance (TCC). The unusually low TCC va lues make these high K dielectrics suitable for application in multila yer ceramic capacitors having EIA specifications Y5P, Y5R and Y5S.