Modulus spectroscopy and dielectric dispersion studies in alkali metal perchlorates

Abstract

Alkali metal perchlorates (KClO₄, RbClO₄, and CsClO₄) undergo a structural phase transition from the orthorhombic to the cubic phase at elevated temperatures. A detailed dielectric study of these crystals across the phase transition is carried out at different frequencies. The crystals are found to exhibit pronounced dielectric dispersion in the kHz frequency range. The results support the view that these transitions are of order–disorder type. The dielectric behaviour at temperatures above T_c is discussed in terms of modulus spectroscopy. An estimate of conductivity relaxation times above the phase transition temperatures made from modulus spectroscopy data gives values of 3.1, 12.2 and 17.7 μs for KClO₄, RbClO₄, and CsClO₄, respectively.