Abstract <p>Comparative studies of the influence of the main operating factors of the spark plasma sintering method on the particle consolidation mechanism, compaction kinetics, and structure of ceramics in the In–Ga–Zn–O oxide system were carried out. Sintering modes were optimized in order to achieve the maximum apparent density of ceramics while maintaining the initial ratio of components by metals. It was found that spark plasma sintering of powder oxide systems occurs with the participation of suboxide phases formed as a result of thermal decomposition and carbothermic reduction of oxides. It was shown that during sintering of zinc oxide-based ceramics under optimized conditions, a nonstoichiometric liquid phase ZnO_{1 – <i>x</i>} is formed on the surface of grains, contributing to the achievement of the full density of the ceramics. At the same time, the hemioxide In₂O formed during sintering of In₂O₃-based ceramics sublimates under the conditions of the experiment without forming a liquid phase and, as a result, its contribution to the particle consolidation processes is significantly lower.</p>