Ceramic Dielectrics with Relatively High Thermal Conductivities

Ceramic dielectrics were prepared by dispersing a high dielectric constant phase in a beryllium oxide matrix. The dispersant phases were doped futile (Ti02) 'rod strontium and calcium til:anate. The microwave dielectric constants varied from 10 to 23 as a function of the amount of dispersed phase. The room temperature thermal conductivity of the same mixture-compositions varied from 0.27 to 0.6 cal/(cm, sec. °C). Mixture equations proved inadequate tcpredict the dielectric constant and thermal conductivity with any significant degree of accuracy. Loss tangents were generally 0.0007, or lower, except for strontium titanate which undergoes a relaxation at microwave frequencies, titus the mixture-loss was raised to 0.0024. The ceramic mixtures sintered to densities typically higher than 97% of theoretical and yielded flexural strengths of the order of 38 000 lbf/in². These values compare favorably with those of single phrase BeO ceramics.