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Effect of Secondary Crystalline Phases on Dielectric Losses in High‐Alumina Bodies
Author(s) -
FLOYD JAMES R.
Publication year - 1964
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1964.tb13813.x
Subject(s) - dielectric , thermal expansion , materials science , mineralogy , alkali metal , flux (metallurgy) , dielectric loss , composite material , chemistry , metallurgy , optoelectronics , organic chemistry
An effort was made to determine the cause of high dielectric losses at 10 6 cps and 25°C in dense, essentially alkali‐free, high‐alumina bodies. Emphasis was placed on secondary crystalline phases in the fired bodies. The flux systems BaO‐SiO 2 , CaO‐MgO‐SiO 2 , and SrO‐SiO 2 were investigated. All high‐alumina bodies having high dielectric losses contained one of the synthetically formed feldspars, BaO.Al 2 O 3 .2SiO 2 , CaO.Al 2 O 3 .2SiO 2 , or SrO.Al 2 O 3 .2SiO 2 . The mechanism by which the feldspars caused the high dielectric losses was tentatively attributed to thermal expansion mismatch. The expansion curves of the feldspars were similar, but they were lower than the expansion curve of alumina.