Dielectric Bodies in the Quaternary System BaTiO ₃ –BaSnO ₃ –SrSnO ₃ –CaSnO ₃

Abstract

Dense bodies were prepared of compositions in the quaternary system BaTiO 3 –BaSnO 3 –SrSnO 3 –CaSnO 3 containing from 3 to 60 mole % stannate. The general effect of the stannate addition to barium titanate was to decrease the Curie temperature and broaden the peak. On a molar basis the three stannates were approximately equivalent in their effect on the dielectric properties of barium titanate, although the rate of shift of the Curie temperature was slightly greater when SrSnO 3 was used. Bodies containing calcium or strontium stannate had lower power factors than those containing barium stannate. Bodies compounded with calcium stannate matured most readily and at lower temperatures. Bodies having dielectric constants ( K ) of 2300 to 2800 at 1 kc. with low positive temperature coefficients up to about 55°C. were obtained with a 3 mole % addition of stannate. Bodies with minimum K 's of 3000 to 4000 at 1 kc. over the range 25° to 85°C. were obtained from BaTiO 3 with an addition of about 6 mole % BaSnO 3 , SrSnO 3 , or CaSnO 3 . Bodies with negative temperature coefficients of K ranging from about 13,000 to about 1000 p.p.m. per °C. were obtained with stannate additions of from 10 to 60 mole %.