Synthesis of a mixed-rare-earth aluminum garnet solid solution

In this work, the substitution of commercial Y2O3 by a rare earth mixed oxide, RE2O3, to form yttrium aluminum garnet (Y3Al5O12—YAG), was investigated. Al2O3:Y2O3 and Al2O3:RE2O3 powder mixtures were milled and pressed. Compacts were sintered at 1000, 1400 or 1600 °C, for 120 min. RE2O3 oxide was characterized by high-resolution X-ray diffraction (HRXRD) and compared to Y2O3. X-ray diffraction pattern of the RE2O3 indicates a true solid solution formation. Rietveld refinement of the sintered YAG and (RE)AG revealed a similar crystal structure. Microstructural analysis of both, YAG or (RE)AG, revealed similar grain sizes of about 2.5 μm and mechanical properties, with hardness of 400 HV and fracture toughness of 3.8 MPam1/2. It could be, thus, demonstrated that pure Y2O3 can be substituted by the rare-earth solid solution, RE2O3, in the formation of YAGs, presenting similar microstructures and mechanical properties.

► Y2O3–Al2O3 and (RE)2O3–Al2O3 powder mixtures.
► Sintering for obtaining yttrium aluminum garnet (YAG).
► Crystallographic characterization — Rietveld Refinement.
► Similarity of mechanical properties.
► Possibility of substitution of yttrium oxide for rare earth oxide mixture at low cost of starting powders.