The rise of dielectric constant and loss tangent in alumina ceramics as they are heated creates serious problems in radome design. This report describes work performed on the first phase of a long range effort to reduce and control this variation in dielectric properties. During the first ten months of the program, attention was concentrated on preparing alumina ceramics of higher purity than is commercially available, and ceramics with low concen¬trations of added impurities. Alumina batches containing less than 100 ppm of foreign cations were prepared by the acid solution of 99.999% aluminum metal, and this material was fired to ceramic discs of similar purity. Specimens were also prepared with introduced Ca and Si at two different levels below 0.1%.
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