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Characterization and Ionic Conductivity Studies on Nano SiO2 Dispersed x NaNO3 - (1-x) Sr(NO3)2 Mixed System

Abstract

Variation of dc ionic conductivity with temperature and mole percent in dispersed mixed ionic conductors of Sodium and Strontium nitrates is presented. The host materials, mixed systems of NaNO3 and Sr(NO3)2 single crystals were grown by solution technique. The powders of different compositions of mixed systems were prepared and then dispersed with SiO2 (10nm) in a particular mole percent. Pellets were made at a pressure of about 5tonnes/sq.m. and sintered at 250oC for 20hours. The room temperature X-ray diffraction patterns of dispersed systems show the co-existence of three phases. The Fourier Transform Infrared spectrum of dispersed systems in the wave number range from 400 to 4000 cm-1 show the existence of three phases and also confirms the existence of OHˉˉ band. In the dispersed systems the enhancement in conductivity is observed to increase with mole percent (m/o) with a threshold at 20.55 m/o where from enhancement starts falling with further increase in mole percent. The maximum enhancement at 20.55 m/o is observed to be above two orders of magnitude with respect to mixed system in the extrinsic conduction region. The enhancement of conductivity in these systems is explained using Maier’s space charge model. The enhancement of conductivity in the dispersed systems is mainly attributed to the increased concentration defects in the space charge layer formed between the host material and the dispersoid. Further, the fall in conductivity may be due to the fall of total effective surface area of contact between the host and dispersoid materials

S Narender Reddy

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