Evaluation of High Permittivity Glass Ceramics for Millimeter Wave Applications.
Final rept. 1 Dec 81-30 Nov 84,
PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF ELECTRICAL ENGINEERING
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The crystallization and dielectric properties of strontium titanate aluminosilicate glass-ceramics, containing perovskite SrTi03 as the primary crystalline phase, have been investigated. The majority of this research was concentrated on glass-ceramics consisting of 65 wt of SrTi03 and 35 wt of silica and alumina with a silicaalumina weight ratio of 21 SAR-2. In glass-ceramics of this composition, the primary crystalline phase was perovskitge SrTi03 other crystalline phases included SrAl2Si208 hexacelsian and anorthite and Ti02 anatase and rutile. the relative amounts of SrTio3 and the other crystalline phases, and the microstructure, were a strong function of the crystallization conditions. The dielectric properties of SAR-2 glass-ceramics were extremely sensitive to the amount of SrTi03 in the glass-ceramic, and thus to the crystallization conditions. Room temperature dielectric constants of the glass-ceramics ranged from 13 to 47. The dielectric constant increased as the crystallization temperature or time was increased, and peaks developed in the dielectric constant at low temperatures. These dielectric constant peaks were not due to dielectric mixing, and it was proposed that the peaks resulted from ferroic domains in the SrTi03, possibly caused by an interaction of the SrTi03 crystallites with the matrix.
- Ceramics, Refractories and Glass
- Electricity and Magnetism