ALKALINE EARTH PORCELAINS POSSESSING LOW DIELECTRIC LOSS*

Abstract

A bstract Alkaline earth porcelains have been prepared from mixtures of clay, flint, and synthetic fluxes consisting of clay calcined with at least three alkaline earth oxides. These porcelains possess excellent dielectric properties, have low coefficients of thermal expansion, are white, and are especially valuable as bases for deposited carbon resistors for which they were developed. Their characteristics make it probable that other uses will be found for materials of this type. An illustrative composition is 50.0% Florida kaolin, 15.0%, flint (325 mesh), 35.0% calcine (200 mesh). The composition of the calcine is 40.0% Florida kaolin, 15.0% MgCO 3 , 15.0% CaCO 3 , 15.0% SrCo 3 , 15.0% BaCO 3 , calcined at 1200°C. The electrical properties of this body at 1 mc. are Q at 25°C., 2160; Q at 250°C., 280; Q at 350°C. 90; specific resistance at 150°C, 10 13.5 ohm‐cm. and at 300°C. 10 10.7 ohm‐cm.