AC conductivity in bismuth oxide doped nickel-zinc ferrites

Abstract

Substituted nickel zinc ferrites have been prepared in the composition series Ni_0.5Zn_0.5Bi_xFe_2.0-xO₄ with x having values in the range 0.05-0.2. The electrical conductivity of the samples has been measured over the temperature range 150 to 300 K at frequencies ranging from 1 kHz to 1 MHz. The ac conductivity shows a variation of ω^s where ω is the angular frequency and s is an exponent having values in the range 0.6 to 0.8. Correlated barrier hopping model is found to be satisfactory in explaining the conductivity which arises due to the presence of Fe²⁺ ions. The latter are created because a substantial amount of Bi³⁺ gets oxidized to the Bi⁵⁺ state.