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Dielectric constants of topaz, orthoclase and scapolite and the oxide additivity rule

Shannon, Robert D. and Oswald, Robert A. and Rossman, George R. (1992) Dielectric constants of topaz, orthoclase and scapolite and the oxide additivity rule. Physics and Chemistry of Minerals, 19 (3). pp. 166-170. ISSN 0342-1791. doi:10.1007/BF00202104.

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The dielectric constants and dissipation factors of topaz, scapolite and orthoclase were determined at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: topaz κ′_a =6.61 tan δ=0.0005 κ′_b =6.82 tan δ=0.0007 κ′_c =6.81 tan δ=0.0007 orthoclase κ′_a =4.69 tan δ=0.0007 κ′_b =5.79 tan δ=0.0007 κ′_c =5.63 tan δ=0.0011 κ′ 11 =4.72 κ′ 22 =5.79 κ′ 33 =5.76 scapolite κ′_a =6.74 tan δ=0.0004 κ′_c =8.51 tan δ=0.0004 The deviation (Δ) between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of ion polarizabilities according to α_D (mineral)=∑α_D (ions) for topaz is 2.5%. The large deviations of orthoclase and scapolite from the oxide additivity rule with δ=+7.2 and + 17.6%, respectively, are attributed to “rattling” K ions in orthoclase and “rattling” (Na,K,Ca) ions and disordered O= and Cl- ions in scapolite.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1992 Springer-Verlag. Received January 23, 1992; accepted May 26, 1992. We thank L.F. Lardear and R.L. Harlow for orientation of the crystals, R.W. Shiffer for sample preparation, C. Foris for obtaining cell dimensions, and J.T. Armstrong and P.K. Carpenter (California Inst. Technology, Pasadena, CA) for microprobe data. We are particularly indebted to Dr. H. Krupp for making the topaz crystals available for study. This work was supported in part by National Science Foundation Grant EAR-86-16064.
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NSFEAR 86-16064
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Deposited On:26 Feb 2014 19:22
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