Effects of molybdenum volume fraction and silica/molybdenum particle-size ratio on relative bulk density and electrical conductivity of silica–molybdenum composites fabricated by spark plasma sintering

SiO₂–Mo composite compact bodies were fabricated by mixing SiO₂ and Mo and then subjected to spark plasma sintering (SPS). In this study, the effects of the volume fraction of Mo and the SiO₂/Mo particle-size ratio of the compact bodies on the relative bulk density and electrical conductivity of the obtained sintered bodies are discussed. The relative bulk density tended to decrease with increasing SiO₂/Mo particle-size ratio and increasing Mo volume fraction, whereas the electrical conductivity increased with increasing SiO₂/Mo particle-size ratio. These results suggest that the density of the regions containing SiO₂ particles in the composite matrix significantly affects the degree of contact between the Mo particles (that form the conduction path). This in turn affects the SPS process, because SPS requires continuous conduction paths for the pulsed direct current to increase the temperature inside the materials. Therefore, when SPS is used to fabricate SiO₂–Mo composite sintered bodies, it is important to select raw material powders that allow the SiO₂/Mo particle-size ratio to be decreased or increased to obtain sintered bodies with high-relative bulk densities or high electrical conductivity, respectively.