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

Abstract

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.

Additional details