Dielectric Constants and Polarizabilities of Ions in Simple Crystals and Barium Titanate

The observed dielectric constants of alkali halides and certain other types of crystals coincide with a relatively simple interpretation of dielectric polarization which is based on the classical equation of Clausius and Mosotti. The polarizability of each elementary ion has only a small positive temperature coefficient and is invariant when the given ion is incorporated in different crystalline solids subject to certain symmetry requirements. The polarizabilities of the ions in cubic barium titanate, although normal, account quite satisfactorily for the high observed values of dielectric constant. A method of estimating dielectric constants from the known polarizabilities of ions is applied to several compounds for which dielectric data have not been reported.