Dielectric ceramic materials with insulated boundaries between crystal grains, and process for preparation

摘要

A dielectric ceramic material composed of primary and secondary ingredients forming in combination a polycrystalline ceramic proper, and of insulating substances diffused throughout the intergranular boundaries of the ceramic proper for an increase in apparent relative dielectric constant. The primary ingredients comprise, in relative proportions, 90.68-99.80 wt. % SrTi03, 0.07-5.32 wt. % of at least one of Nb205, W03 and Ta2O5, and 0.02-4.00 wt. % of at least one of GeO2, ZnO and CuO. The secondary ingredients comprise 0.02-0.10 wt. part Si02 and 0.01-0.03 wt. part Al2O3 with respect to 100 wt. parts of the primary ingredients, with the weight ratio of Si02 to Al2O3 being from 1.5 to 5.0. The insulating substances comprise 0.02-2.90 wt. % PbO, 0.10-4.38 wt. % Bi2O3, and 0.001-0.18 wt. % B203 with respect to the total weight of the primary and the secondary ingredients. In the fabrication of bodies of the ceramic the mixture of the insulating substances is coated or otherwise layered on polycrystalline ceramic bodies prepared from the primary and secondary ingredients. The coated ceramic bodies are then heated to cause diffusion of the insulating substances throughout their intergranular boundaries.