A coated member comprising a substrate of Mo, Ta, W, Zr or carbon and a coating of rare earth-containing oxide including a surface layer having a Vickers hardness of at least 50; or a coated member comprising a substrate having a coefficient of linear expansion of at least 4.times.10.sup.-6 (1/K) and a coating of rare earth-containing oxide thereon is heat resistant and useful as a jig for use in the sintering of powder metallurgical metal, cermet and ceramic materials.