A.C. Conductivity Investigations on Layered Na2-x-yLixKyTi3O7 Ceramics

Abstract

Frequency and temperature dependence of a.c. electrical conductivity of layered mixed ionic alkali trititanates, Na1.89Li0.10K0.01Ti3O7, Na1.88Li0.10K0.02Ti3O7, Na1.86Li0.10K0.04Ti3O7, and Na1.85Li0.10K0.05Ti3O7, have been investigated over a wide temperature 350 K ≤T≥ 725 K and frequency 10 kHz to 1 MHz range. For this, Arrhenius plots are used for a.c. electrical conductivity of these compounds. The obtained conductivity plots have been divided into four distinct regions and discussed the relevant theory. According to slop variation, the conduction mechanisms occurring are different in different temperature regions. At lower temperatures, the hopping electron disorders the surroundings by moving to its neighboring Ti atoms from their equilibrium positions, causing structural defect in the polycrystalline network named small polaron. At higher temperatures, associated/unassociated interlayer ionic conduction occurs along with the alkali ions hopping through the interlayer space and electron hopping (small polaron) conduction through Ti–Ti chains in these layered polar alkali titanates.