A NOVEL METHOD FOR THE UNIFORM INCORPORATION OF GRAIN-BOUNDARY LAYER MODIFIERS IN POSITIVE TEMPERATURE-COEFFICIENT OF RESISTIVITY BARIUM-TITANATE

The presently developed two-stage process involves dipping the prefired porous disks of n-BaTiO3 in nonaqueous solutions containing Al-butyrate, Ti-isopropoxide, and tetraethyl silicate and subsequent sintering. This leads to uniform distribution of the grain-boundary layer (GBL) modifiers (Al2O3 + TiO2 + SiO2) and better control of the grain size as well as the positive temperature coefficient of resistivity characteristics. The technique is particularly suited for GBL modifiers in low concentrations (< 1%).