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Effect of Porosity and Grain Size on the Microwave Dielectric Properties of Sintered Alumina
Author(s) -
Penn Stuart J.,
Alford Neil McN.,
Templeton Alan,
Wang Xiaoru,
Xu Meishing,
Reece Michael,
Schrapel Kevin
Publication year - 1997
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.1151-2916.1997.tb03066.x
Subject(s) - materials science , porosity , grain size , crystallite , impurity , composite material , dielectric , permittivity , volume (thermodynamics) , mineralogy , grain boundary , microstructure , metallurgy , thermodynamics , chemistry , physics , optoelectronics , organic chemistry
The real part of the permittivity (ε) and the tan δ of sintered alumina (Al 2 O 3 ) at about 9 GHz have been measured. The dielectric properties have been examined as a function of purity, pore volume, and sintered grain size. The tan δ is found to depend very strongly on the pore volume, purity, and grain size. ε is far less sensitive to impurities and grain size. The dependence of ε on porosity can be described by simple mixture models as expected. A model of losses in single crystals cannot be extended easily to these materials where extrinsic factors such as porosity, random crystal orientation, grain boundaries, microcracks, and impurities dominate. These factors have been studied in an attempt to describe the tan δ and ε of sintered polycrystalline alumina. In this work, the tan δ for alumina has been studied in near‐theoretical density ranges between 9.1 times 10 ‐5 and 2.4 times 10 ‐5 depending on grain size.