Flash-sintering of MnCo2O4 and its relation to phase stability

The flash-sintering behavior of manganese cobaltite spinel (MnCo2O4) is analyzed in the present work. It is shown that the MnCo2O4 is flash-sintered at 120-150°C under 15.0-17.5Vcm-1, which is substantially lower than the conventional-sintering temperatures of 1080°C and more. We have also demonstrated that the flash-sintering is a transient phenomenon, where the power dissipation rises quickly at first and then results to Joule heating. The extent of sintering is confirmed through SEM, where a dense and pore-free morphology is observed for the well-sintered samples. The growth of secondary phase as a function of sintering temperature in both conventional and flash processes is monitored by XRD. Consistent changes in I-V curves observed at 200-700°C, suggest that the rapid increase of the conductivity during flash-effect follows the hopping mechanism of usual conductivity phenomenon. On the basis of correlation between the conductivity, phase-stability and microstructure, a mechanism for flash-sintering has been proposed. © 2014 Elsevier Ltd.