ac impedance measurements and <i>V</i>-<i>I</i> characteristics for Co-, Mn-, or Bi-doped ZnO

Abstract

ZnO has been doped with various oxides, mainly bismuth, cobalt, and manganese oxides. The aim of the present approach is to look at the influence of each dopant on the electrical behavior of ZnO in a system which is more simple and chemically purer in comparison with commercial varistors. It appears that cobalt or manganese additions do not substantially modify the bulk conductivity of ZnO. Also these dopants by themselves do not lead to a varistor effect when the material is subjected to a potential sweep. On the other hand, bismuth-based compositions behave like varistors. The best performances have been recorded for a simultaneous doping with manganese and bismuth.