Alternating current conductivity of the interfacial phase in copper oxide-silica gel nanocomposites

A nanocomposite structure was induced in gel of composition 60CuO . 40SiO(2 ) (mol%) by first of all precipitating nano-sized copper particles by a red uction treatment and subsequently subjecting these to a controlled oxidatio n treatment, The particle size was of the order of 6.8 nm, Alternating curr ent (ac) conductivity measurements were carried out on different specimens in the temperature range 300 to 630 K covering a frequency spectrum 0.1 kHz to 2 MHz, The ac conductivity was found to have a variation with frequency given by omega (s), omega being the angular frequency and s the frequency exponent, The analysis of the variation of s as a function of temperature l ed to the conclusion that an overlapping large polaron tunneling mechanism was operative in this system, The effective barrier height for polaron tran sfer for infinite intersite separation was found to be almost twice in the case of the precursor gel as compared to that for the composite with the in terfacial amorphous phase.