Current–voltage characteristics and grain growth of Li2CO3-doped tungsten trioxide ceramics

Ceramics samples of tungsten trioxide doped with lithium carbonate from 0.5 to 5 mol% were prepared by conventional electroceramic technique. The current–voltage characteristics of these ceramics were measured under various ambient temperatures. All of the I–V curves showed non-ohmic electrical properties with obvious negative-resistance characteristic at room temperature. It is found that there exists a direct correlation between the negative-resistance phenomenon in the I–V curves and the electrical history of these samples. The suitability of some models regarding the negative-resistance characteristics is discussed. X-ray diffraction (XRD) revealed coexistence of two phases of tungsten trioxide, which depends on the amount of lithium. Scanning electron microscope (SEM) showed great differences for both grain shape and size between the Li-doped and undoped WO3 ceramics, and this indicates that Li2CO3 doped into WO3 influences strongly the growing of WO3 during sintering process.