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Dielectric Properties of Alumina at High Temperatures
Author(s) -
FLORIO JOHN V.
Publication year - 1960
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.1151-2916.1960.tb14594.x
Subject(s) - crystallite , materials science , dielectric , activation energy , conductivity , electrical resistivity and conductivity , atmospheric temperature range , single crystal , thermal conduction , dissipation factor , condensed matter physics , impurity , crystal (programming language) , analytical chemistry (journal) , composite material , chemistry , thermodynamics , crystallography , metallurgy , optoelectronics , electrical engineering , engineering , programming language , physics , organic chemistry , chromatography , computer science
The dielectric constant and dissipation factor of both single‐crystal and polycrystalline alumina were measured in air over the frequency range lo 2 to 3 × 10 5 cycles per second, in the temperature interval 900° to 1300° C. The three‐electrode guard‐ring method was used. The observed dielectric losses were due predominately to free‐electron conduction mechanisms. The volume conductivity of single‐crystal and polycrystalline alumina was calculated from the high‐frequency data. The temperature dependences of the volume conductivity for two single crystals of different thicknesses were similar. The large thermal activation energy indicated intrinsic conductivity; the energy band gap of alumina was calculated to be approximately 7.3 electron volts. The bulk conductivities of the polycrystalline alumina were considerably higher than the single‐crystal values, presumably because of impurities in the polycrystalline material. The results were compared with values previously reported in the literature.