Microwave High Dielectric Constant Materials.
Final technical rept. 1 Jul 69-28 Feb 71,
RAYTHEON CO WALTHAM MASS RESEARCH DIV
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The intent of the program was to develop high dielectric constant, temperature compensated microwave ceramic materials. The approach used was to form two-phase bodies consisting of a titanate phase and rutile as the second phase. Empirical mixing rules predict that by mixing two dielectrics, one having a positive temperature coefficient and the other negative, a compensated material can be achieved at one particular composition. The microwave properties of rutile had been investigated and was found to have a very negative coefficient. Therefore, the initial phase of the program was to find titanate compounds having positive temperature coefficients to form a two-phase mixture with TiO2. As a result of this phase of the program four essentially temperature-insensitive high-dielectric-constant materials were developed. They are BaTi4O9, Li2O 1.5 TiO2, 84 percent MgTi2O5 - 16 percent TiO2, and a Zn2TiO4 - TiO2 mixture. Later in the program, a non-compensated material having a dielectric constant near k 50 was desired. Therefore, a two-phase mixture of 72 percent BaTi4O9 - 28 percent TiO2 was developed to satisfy this requirement. Microwave dielectric properties were measured on all of these materials, as well as thermal expansion coefficient, modulus of rupture, hardness, and water absorption. During the final phase of the program, pilot plant quantities of BaTi4O9 and the 72 percent BaTi4O9 - 28 percent TiO2 material were fabricated and delivered. Author
- Ceramics, Refractories and Glass