In this preliminaries studies, Si3N4-SiC(w) containing rare earth concentrate (CTR) have been evaluated, aiming analyze their utilization as sintering aids, in ceramics composites. The compositions were hot uniaxial pressing sintered in nitrogen atmosphere, at 1750degreesC during 30 min and heating rate off 20degreesC/min, under 20 MPa pressure. Specific mass was determined according to ASTM C20-87 and crystalline phases were identified by X-ray diffraction. The microstructural analysis were performed using scanning electron microscope. Microhardness and fracture toughness values have been determined at room temperature, using Vickers indenter, taking an average of five indentations in each composition. The viability of the rare earth concentrate as sintering aids and their effects on densification process and mechanical properties are discussed.