Alumina ceramics were joined by hot‐pressing with polystyrene or mica sheets at temperatures of 1250° or 1350°C. The polystyrene decomposed during hot‐pressing, creating reducing conditions in the joints which enhanced interfacial diffusion and bonding. Measured fracture toughness and flexural strength of such joints approached values for monolithic alumina. Joints prepared under similar conditions but without polystyrene showed much lower KICand strength v