Sol–gel synthesis of doped nanocrystalline ZnO powders using xanthan gum and varistor properties study

Abstract

ZnO–Co₂O₃–Bi₂O₃ nanocomposites were synthesized by sol–gel method with the aid of xanthan gum as a polymerization agent instead of any organic additives. Xanthan gum was polymerization agent to terminate the growth of doped nanocrystalline ZnO powders and then stabilize them. Spherical and hexagonal doped nanocrystalline ZnO powders with particle size of about 20–45 nm were easily obtained in the presence of xanthan gum. The results showed that ZnO nanopowders were doped in additional metal oxides and Bi_7.5Co_0.47O_11.92 phase was observed at the as-prepared ZnO nanopowders after calcined at 500 and 600 °C. The varistor ceramics sintered at 1150 °C for 2 h in air have a density of 5.52 g/cm³ corresponding to 95.5 % of the theoretical density with breakdown voltage of 3100.91 V/cm and nonlinear coefficient of ~27.19. The experimental results showed the advantage of addition of the xanthan gum for avoiding hard agglomeration and improving electrical performance of the varistors.