LOW-VOLTAGE VARISTORS BASED ON ZINC ANTIMONY SPINEL ZN7SB2O12

It is possible to prepare low-voltage varistors from the zinc antimony spinel Zn7Sb2O12 with breakdown voltages in the range of 3-20 V and n onlinearity coefficient alpha=7-15. The varistor property is due to th e formation of high ohmic potential barriers at the grain boundary reg ions on low-ohmic n-type grain interiors of the polycrystalline sample s. The method of preparation of the spinel, synthesized by coprecipita tion followed by annealing under restricted partial pressures of oxyge n, controls the mixed valence states for antimony, namely, Sb3+ and Sb 5+. This is critical in attaining high nonlinearity and lower breakdow n voltages. (C) 1996 American Institute of Physics.