Ultrafine-grained non-oxide ceramics were prepared by combining the synthesis technology for fine-grained starting powders and the rapid sintering technology for spark plasma sintering (SPS); the two technologies were combined for obtaining ceramics with improved heat and corrosion resistance and improved mechanical properties. Hollow spherical Ca-α SiAlON powders composed of nanosized particles were synthesized by carbothermal reduction–nitridation of a SiO₂–Al₂O₃–CaCO₃ powder mixture. Using the Ca-α SiAlON powder, dense Ca-α SiAlON nanoceramics and porous Ca-α SiAlON ceramics with excellent mechanical properties and high heat and corrosion resistance were fabricated by the SPS technique. Ultrafine-grained Si₃N₄ and SiC ceramics were prepared from fine-grained Si₃N₄ and SiC powders by SPS. The densification of cubic-BN-dispersed ceramics composites was achieved without the phase transformation of cubic BN to low-hardness hexagonal BN, at a moderate pressure by the SPS technique.