THE INFLUENCE OF MECHANO ACTIVATION ON THE STRUCTURE AND ELECTRICAL CONDUCTIVITY IN THE SYSTEM KNO3-Al2O3

Abstract

In this paper, the effect of mechanical activation on the structure and electrical conductivity of the KNO3-Al2O3 composite was studied. Based on the analysis of DSC curves measured during heating and cooling of the sample, it was found that the enthalpy of phase transitions decreases with increasing time of mechanical activation of the 0.5KNO3-0.5Al2O3 composite. X-ray diffraction analysis shows that mechanical activation leads to a decrease in the grain dimension and an increase in the defectiveness. Based on the electrochemical impedance spectroscopy data, it was determined that for the KNO3-Al2O3 system subjected to mechanical activation, the values of specific ionic conductivity are 3.8×10-5 S/cm at T = 373 K and 2×10-3 S/cm at T = 473 K and the energy value activations of 0.19 eV are comparable with the parameters of a composite of the same chemical composition obtained by the ceramic technique. Raman spectroscopy revealed the formation of a metastable γ-phase KNO3during the mechanoactivation of the composite, which is stable at temperatures above 397 K. It is proposed that an increase in electrical conductivity in the KNO3-Al2O3 composite at 373-403 K is due to the presence in the composite of an additional metastable γ-phase KNO3.