Effects of Sintering Processes on Microstructure Evolution, Crystallite, and Grain Growth of MoO 2 Powder.

MoO₂ micro-powders with a mean pore size of 3.4 nm and specific surface area of 2.5 g/cm³ were compacted by dry pressing, then pressureless sintered at a temperature of 1000–1150 °C for 2 h or for a sintering time of 0.5–12 h at 1050 °C in an N₂ atmosphere. Then, their microstructure evolution for morphology, crystallite, and grain growth were investigated. By sintering at a certain temperature and times, the irregular shape of the MoO₂ powders transformed into an equiaxed structure, owing to the surface energy, which contributed to faster grain growth at the initial stage of sintering. The crystallite and grain sizes exponentially increased with the sintering time, and the growth exponent, n, was approximately 2.8 and 4, respectively. This indicates that the crystallite growth is governed by dislocation-mediated lattice diffusion, and the grain growth is determined by surface diffusion-controlled pore mobility. The increase in sintering temperature increased both crystallite and grain size, which obeyed the Arrhenius equation, and the activation energies were determined to be 95.65 and 76.95 kJmol⁻¹ for crystallite and grain growths, respectively. [ABSTRACT FROM AUTHOR]