Decoupling the effects of pressure and current in spark plasma sintering: Synthesis of CU0.9V2O5

The synthesis of ε-Cu0.9V2O5 prepared from Cu + V2O5 powder mixtures by spark plasma sintering (SPS) and conventional solid-state synthesis are compared. Preparations by SPS proceed much more quickly than reactions of loose powder in sealed tubes, which would seem to result from the effect of uniaxial pressure on promoting inter-particle contact between reacting powders. This explanation is consistent with the observation of rapid reactions in pre-compacted pellets heated in sealed tubes. However, a hotly debated topic within the SPS community is the possible role of the electric current in promoting reaction rates. Here, we describe studies in which the influence of these two parameters, pressure and current, has been studied independently. Our results show that the uniaxial pressure has no intrinsic role in affecting the rate of formation of ε-Cu0.9V2O5, and suggest that the current plays little or no role other than facilitating rapid heating of the sample.