Abstract
Dielectric relaxation spectroscopy (DRS) was carried out on hydrated NaA zeolite (LTA) with various high pretreatment temperatures (PT), and the effect of thermal treatment on crystal structure was characterized by X-ray diffraction analysis (XRD). A dielectric relaxation about 10 5 Hz was found to be closely related to the integrity of the pore framework, and the decreased relaxation increment was attributed to the structural evolution of LTA. The critical temperature (CT), where the crystal structure of LTA starts to essentially change, was jointly determined by DRS and XRD. Comprehensive investigation of the relaxation mechanism and time indicated symmetrical shrinkage of pore channels at thermal PT below CT. The Hanai method was used to calculate the dielectric properties of LTA particles and aqueous medium. The invariant permittivity of particles indicated the thermal stabilization of polarization distribution of sodium ions, and the decreased particle conductivity with PT increasing to CT reflected the negative effect of thermal pretreatment on the mobility of sodium ions. The abnormal conductivities of particles and medium indicated prior sintering on the pore's surface at the beginning of crystal structure transition.
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