PURPOSE: To produce a ceramic product such as a laser cathode uniformly and free from extraneous materials by sintering a green wear shape of mixed metal oxide obtained by burning a carbonate obtained by allowing quat. ammonium carbonate to react with a metal ion and precipitating.

CONSTITUTION: The aqueous quat. ammonium carbonate is allowed to react with the metal ion to precipitate a water-insoluble carbonate. The metal oxide consisting of more than one kind among the groups of rare earths, and alkaline earths, (Cu, Ag, Au), (Mn, Fe, Co, Ni), (Zn, Cd, Hg), (Pd, Bi), (Sc, Y) and Zr is obtained by burning the precipitate. Then, the mixture of this oxide is formed to make a green wear shape and to make it dense by pressurizing it at ≥10000 psi pressure. Then the formed material is sintered to obtain an end ceramic product uniform at the atomic level and free from the extraneous materials.