In the same conditions, the dielectric constant of the nano-ceramic precursor WO3 is an order of magnitude higher than micro Mickey WO3 ceramics, while the sintering atmosphere of air can increase the dielectric constant by one order of magnitude. The non-linear electrical properties of polycrystalline WO3 ceramics and other varistors (ZnO, Ti02, etc.), can be explained by Schottky barrier model. WO3 grains express as an n-type semiconductor behavior due to the presence of oxygen vacancy.
A large number of experimental studies suggest that the appearance of non-linear electrical characteristics a certain relationship to WO3 two-phase coexistence at the normal temperature, it’s believed that coexistence phase will affect the matching of crystal lattice, so that the grains have different dielectric responses. Samples sintered in air have coexistence structure of monoclinic and triclinic two-phase, having a non-linear current characteristic, and the samples sintered in a hydrogen atmosphere only have monoclinic structure, of which the voltage characteristics are linear, but also to some prove the extent of the conjecture that phase coexistence of WO3 ceramics at room temperature led to the production of Schottky barrier, so that the WO3 ceramics have nonlinear voltage characteristics.