AC CONDUCTIVITY IN BISMUTH OXIDE DOPED NICKEL-ZINC FERRITES

Substituted nickel zinc ferrites have been prepared in the composition series Ni0.5Zn0.5BixFe2.0-O-x(4) with x having values in the range 0. 05-0.2, The electrical conductivity of the samples has been measured o ver the temperature range 150 to 300 K at frequencies ranging from 1 k Hz to 1 MHz. The ac conductivity shows a variation of omega(s) where o mega is the angular frequency and s is an exponent having values in th e range 0.6 to 0.8. Correlated barrier hopping model is found to be sa tisfactory in explaining the conductivity which arises due to the pres ence of Fe2+ ions. The latter are created because a substantial amount of Bi3+ gets oxidized to the Bi5+ state.