Dielectric properties of dehydrated NaA zeolite, analyses and calculation of dielectric spectra

Abstract

Dielectric spectra (ε′, ε″ and tan δ) of dehydrated NaA zeolite were measured in the temperature range 330–510 K and analyzed in detail to determine the characteristic values (ε_s, ε_∞, β and peak frequency) of the dielectric relaxations. Two relaxations caused by Na⁺ ion as an exchangeable cation were measured in the spectra and the relaxations on the lower and higher frequency sides had activation energies of 60 and 49 kJ mol⁻¹, respectively. By using the optimum characteristic values determined, the spectra of ε′, ε″ and tan δ at each temperature were calculated, and each calculated spectrum was in good agreement with the measured spectrum. The temperature dependences of all characteristic values were determined and hence it was possible to calculate the spectra at various temperatures. The characteristic values were also estimated by plotting the measured data on the Cole–Cole plane and separating the Cole–Cole curve separated into three parts including two circular arcs. The characteristic values estimated by this method were not in agreement with those determined by the former method. The limitations of the latter method are discussed.