Conductivity studies on microwave synthesized glasses using complex impedance spectroscopy

Abstract

Microwave Synthesis of fast ion conducting glasses offers advantage of efficient transformation of energy and heating throughout the volume efficiently in a short time. Lithium ion transport process in a modified glass network doped with lithium salt have been studied in a wide range of compositions with a general formula xLi 2 SO 4 -(100-x) [0.80 LiPO 3 : 0.20 MoO 3 ] where x ranges from 0 to 25 mol%. Frequency and temperature dependent conductivity measurements have been carried out in the frequency range of 10 Hz to 10 MHz and a temperature range of 313K -353K. Conductivity in these glasses is governed by the incorporation of lithium salt in the macromolecular structure, which results in the expansion of the network structure of glass. Impedance spectra of these glasses show a single semicircle and dc conductivities are extracted from it. Activation energies (E dc ) calculated using regression analysis of Arrhenius plots decreases while conductivity ( dc ) increases with increasing LiSO 4 mol%. Increased conductivity is due to gross structural changes initiated by the network modification and incorporation of SO 4 2-ions. The complex impedance data have been analyzed using dielectric modulus formalism to study the relaxation dynamics of the charge carriers in the investigated glasses. The observed ac conductivity spectra follow Almond-West's single power law ( ) = (0) + A s and the relaxation mechanism in these glasses are analyzed using Kohlrausch-Williams-Watts (KWW) stretched exponential function. Dynamic conductivity spectra, ( ) convey information about the ion dynamics occur in a time window given by the inverse angular frequency. IntroductionAs an emerging material processing technique, microwave heating has attracted increasing interest in material processing and synthesis of amorphous nanoparticles. It was applied widely to produce superconductors, Ferro-electric ceramics, Carbides, Nitrides etc. because of its great flexibility for thermal treatment which influences the microstructure of materials. Microwave heating has the potential for overcoming problems encountered in conventional processes. Since the energy is absorbed directly by the bulk of the material, rather than being conducted from outside, uniform and rapid heating can be achieved within a short time and at a temperature much lower than normally required. Moreover, energy consumption and processing time are reduced significantly. The important reasons for this are the continuing need for fast and energy-saving techniques, and the synthesis of metastable, phases by passing thermodynamically reversible routes. Though microwave synthesis is quite faster, simpler and energy efficient, the exact nature of microwave interaction with reactants during synthesis of materials is unclear and speculative.Lithium based fast ionic electrolytes have gained much attention because of their potential technological applications such as lithium ion batteries, electro chromic displays, gas sensors etc [1-3]. Glassy electrolytes have many advantages over thei...