Slater's theory of the dielectric constant in BaTi${\mathrm{O}}_3$ has been extended by treating the ionic polarizability quantum mechanically instead of classically. This leads to an expression for the dielectric constant which is good at all temperatures and shows a deviation from the Curie-Weiss law at low temperatures. The theory is applied to SrTi${\mathrm{O}}_3$ and to KTa${\mathrm{O}}_3$ above its transition at 13.2°K.

• Received 26 December 1951

DOI:https://doi.org/10.1103/PhysRev.86.118