Dielectric Constant in Paraelectric Perovskites
Abstract
The relative dielectric constant of a series of perovskites such as CaTiO_{3}, SrTiO_{3}, BaTiO_{3}, PbTiO_{3}, and KTaO_{3} has been measured at microwave frequencies over a wide range above the Curie temperature. It was found that a CurieWeiss law of the form ∊=∊_{L}+C(TT_{c}) is accurately obeyed where ∊_{L} is of the order of 50 and represents the dielectric constant in the limit of infinite temperature, and that T_{c} and C, the Curie temperature and Curie constant, increase monotonically with increasing cation mass. ∊_{L} consists of contributions from the electronic polarizability, temperatureindependent optically active lattice vibrations, and a dominant term stemming from the finite frequency of the temperaturedependent soft mode in the limit of infinite temperature. The limiting frequency of the "soft mode" at high temperatures is estimated.
 Publication:

Physical Review
 Pub Date:
 August 1964
 DOI:
 10.1103/PhysRev.135.A748
 Bibcode:
 1964PhRv..135..748R