The interface reactions between an α/gb-sialon ceramic and Cu, Cu2O or a Cu-Cu2O mixture have been studied. A fully dense sialon ceramic material prepared by pressureless sintering at 1775 ° C with 6 wt% Y2O3 as sintering aid, were coldpressed together with Cu, Cu2O or Cu-Cu2O mixtures into cylindrical tablets. These samples were heat treated at 700, 850 and 1000 ° C in evacuated silica tubes. The reaction zones formed between the sialon and the powder compacts were studied in a SEM equipped with an EDS system. No reaction between copper and sialon ceramic could be detected in spite of prolonged heat treatment at 1000 ° C. Cu2O reacted with the ceramic at 850 and 1000 ° C to form a glass containing copper and all the other sialon components. The interaction between the sialon material and the Cu-Cu2O powder compacts was characterized by a redox reaction. The sialon was thus oxidized to SiO2 and N2 while Cu2O was reduced to copper. A glass phase containing silicon, aluminium, yttrium and copper was also formed in the reaction.