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Published 1991 | public
Journal Article

Dielectric constant of MgAl_2O_4 spinel and the oxide additivity rule

Abstract

The dielectric constants and dielectric loss values of five natural and three synthetic spinel single crystals were determined at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: Mg_(1.02)AI_(1.98)Fe_(0.01)O_4 K'=8.355 tan δ=0.0005 Mg_(1.00)AI_(1.98)Fe_0.02)O_4 K'=8.322 tan δ=0.0007 Mg_(1.00)AI_(1.99)Fe_(0.02)O_4 K'=8.203 tan δ=0.0007 Mg_1.01)Al_(1.98)O_4 K'=8.352 tan δ=0.0005 Mg_(0.97)AI_(2.01)Fe_(0.01)O_4 K'=8.302 tan δ=0.0005 Mg_(1.00)AI_(2.00)O_4 K'=8 tan δ=0.0008 Mg_(1.00)AI(2.00)O_4 K'=8.176 tan δ=0.0005 Mg_(0.415)Al_(2.39)O_4 K'8.572 tan δ=0.0011. The agreement between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to α_D(mineral) = Σ_(αD)(oxides) for this group of spinels ranges from + 1.1 to + 3.2%, well above the agreement value of 0.5–1.0% found for well-behaved oxides. Possible reasons for these discrepancies are discussed.

Additional Information

© 1991 Pergamon Press. Received 28 January 1991; accepted 21 March 1991. We thank R. W. Shiffer for sample preparation, A. Brown (Studsvik Energiteknik AB, Nykoping, Sweden) and C. Foris for obtaining cell dimensions, J. C. Calabrese for converting anisotropic to isotropic temperature factors, and J. T. Armstrong (California Inst. Technology, Pasadena, CA) for microprobe data. This work was supported in part by National Science Foundation Grant EAR-86-18200.

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023