Fine grained batio.sub.3 powder mixture and method for making

Abstract

Disc and monolithic (multilayer) ceramic capacitors having a fine grained barium titanate body exhibit a high dielectric constant and a smooth (X7R) temperature coefficient of capacitance. The start ceramic materials for making such capacitors are predominantly spherical barium titanate powder particles of average particle size less than 0.7 micron and of narrow particle size distribution. The barium titanate is mixed with around 2 weight percent of a the cadmium silicate flux, 3Cd.SiO.sub.2, serving as a reactivity and sintering promoting agent; and about one weight percent of a reactivity and sintering inhibitor agent, Nb.sub.2 O.sub.5. After preparing a green body of this mixture, the body is sintered at about 1100.degree. C. A powder mixture for manufacture of such capacitors includes mixing powders of the three above-described materials, mildly sintering the powder mixture and if necessary comminuting the calcine to produce a ceramic powder of agglomerates of the start powders, each agglomerate having the same composition as did the precursor mixture. Low firing monolithic ceramic capacitors have been made with 70% Ag 30% Pd buried electrodes and with ten microns thick active ceramic dielectric layers having a dielectric constant (K) of 4800 and a temperature coefficient well within the X7R range.