Dielectric constants of diaspore and B-, Be-, and P-containing minerals,

the polarizabilities of B₂O₃ and P₂O₅, and the oxide additivity rule

ROBERT D. SHANNON, MUNIRPALLAM A. SUBRAMANIAN

Central Research Department, Experimental Station 356/329, E.I. Du Pont de Nemours
Wilmington, Delaware 19880-0356, U.S.A.

ANTHONY N. MARIANO

48 Page Brook Road, Carlisle, Massachusetts 01741, U.S.A.

THURMAN E. GIER

P.O. Box 884, Chadds Ford, Pennsylvania 19317, U.S.A.

GEORGE R. ROSSMAN

Division of Geological and Planetary Sciences, California Institute of Technology
Pasadena, California 91125, U.S.A.

ABSTRACT

The 1-MHz dielectric constants and loss factors of the minerals diaspore, euclase, ham bergite, sinhalite, danburite, datolite, beryllonite, and montebrasite and of the synthetic oxides La₂Be₂O₅, A1P₃O₉, and NdP₅O₁₄ were determined. The dielectric polarizabilities of B₂O₃ and P₂O₅ derived from the dielectric constants of these compounds are 6.15 and 12.44 Å3, respectively. The dielectric constants of the above minerals and oxides, along with the dielectric polarizabilities of Li₂O, Na₂O, BeO, MgO, CaO, A1₂O₃, Nd₂O₃, La₂O₃, SiO₂, diaspore, and the derived values of the polarizabilities of B₂O₃ and P₂O₅, were used to calculate dielectric polarizabilities from the Clausius-Mosotti equation and to test the oxide additivity rule. The oxide additivity rule is valid to ± 0.5% for all except beryllonite. These compounds with deviations from additivity of 0.5-1.5%, along with previously studied aluminate and gallate gamets, chrysoberyl, spinel, phenacite, zircon, and olivine- type silicates, form a class of well-behaved oxides that can be used as a basis for compar ison of compounds that show larger deviations (>5%) caused by ionic or electronic conductivity, the presence of H₂O or CO₂, or structural peculiarities.

American Mineralogist, Volume 77, pages 10 1-106, 1992