HIGH TEMPERATURE THICK FILM DIELECTRICS
Abstract
High temperature dielectric materials are needed for geothermal well logging electronics. A review of dielectric properties of some inorganic materials, theoretical calculations for the dielectric properties of multiphase systems and previous high temperature work concerning dielectric materials are summarized in this thesis. Crystallizable glass was found to be potentially applicable as a low k, high temperature dielectric. Temperature compensated, multiphase systems are believed to be necessary for a medium k, high temperature dielectric. Two high temperature glass frits, Frit 1B (29 m/o PbO - 36.9 m/o B(,2)O(,3) - 20.4 m/o SiO(,2) - 13.7 m/o Al(,2)O(,3)) and Frit 2A (21 m/o CaO - 9 m/o BaO - 38 m/o B(,2)O(,3) - 20 m/o SiO(,2) - 12 m/o Al(,2)O(,3)), were developed for use in thick film dielectrics. A low k (k (TURNEQ) 10) dielectric containing 35 w/o Frit 1B, 40 w/o Frit 2A and 25 w/o (alpha)Al(,2)O(,3) was developed for use to 500(DEGREES)C with a lifetime in excess of 1000 hours. In a thick film format, the increase in dielectric constant from 25(DEGREES)C to 500(DEGREES)C was less than 15%, and the dissipation factor (10 kHz) at 500(DEGREES)C was less than 4%. A medium k dielectric consisting of 35 v/o Frit 1B - 25 v/o SrTiO(,3) - 40 v/o BaTiO(,3) was developed for high temperature use in thick film capacitors. This composition showed a change in dielectric constant of less than 12% to 350(DEGREES)C, and a dissipation factor (1 kHz) of less than 12% at 350(DEGREES)C. When properly heat treated before application, capacitors made with this composition showed a capacitance change of less than 6% after 1000 hours at 500(DEGREES)C.
Degree
Ph.D.
Subject Area
Materials science
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