The effect of TiO₂ concentration on the electrical and microstructural properties of ZnO-base varistor ceramic prepared from nanosize ZnO particles

ABSTRACT

This study investigated electrical properties and microstructure of zinc oxide varistors containing MnO₂, Cr₂O₃, V₂O₅ and TiO₂. To this end, nanosize ZnO particles were synthesised by the polyacrylamide-gel method and doped with minor amounts of MnO₂ (0.5 mol-%), Cr₂O₃ (0.5 mol-%), V₂O₅ (2 mol-%) and TiO₂ in the range of 2–15 mol-%. The prepared samples sintered at 1050°C in air for 2 h. It was observed that TiO₂ promoted grain growth of ZnO particles. X-ray examination showed hexagonal ZnO structure as a main phase and Zn₂TiO₄ and ZnV₂O₄ as minor secondary phases. The nonlinear coefficient and threshold voltage of the prepared samples were in the range of 3.3–7.9 and 1120–4700 V cm⁻¹ respectively, in which both of them increased with increase in TiO₂ content. Among the prepared samples, the varistor with 15 mol-% TiO₂ exhibited the best performance in terms of nonlinearity. The nonlinear electrical behaviour was explained by theory of formation of the potential barriers at grain boundaries.

KEYWORDS:

• Ceramic
• nano ZnO powder
• varistor
• TiO₂
• nonlinear coefficient

Disclosure statement

No potential conflict of interest was reported by the author(s).