Single-phase Y₄Al₂O₉ (YAM) powders were synthesized via solid-state reaction starting from nano-sized Al₂O₃ and Y₂O₃. Fully dense (99.5%) bulk YAM ceramics were consolidated by spark plasma sintering (SPS) at 1800 ℃. We demonstrated the excellent damage tolerance and good machinability of YAM ceramics. Such properties are attributed to the easy slipping along the weakly bonded crystallographic planes, resulting in multiple energy dissipation mechanisms such as transgranular fracture, shear slipping and localized grain crushing.