Using wet chemistry techniques, ultrafine powders of complex oxides Y2.5Nd0.5Al5O12 (YAG) have been obtained with the garnet structure and coated with layers of nickel by means of precipitation from salt solutions. Spark Plasma Sintering (SPS) was used to obtain fine-grain ceramic composites YAG Ni with 92-99% density. Sintering activation energies were determined and it was demonstrated that the intensity of high-rate sintering of the investigated ceramic composites is determined by the intensity of the nickel creep at lower heating temperatures, the intensity of oxygen diffusion in the garnet crystal lattice at average SPS temperatures, and the intensity of grain boundary diffusion at high SPS temperatures. (C) 2018 Published by Elsevier B.V.