Structural and morphological studies on yttrium-doped magnesium aluminate spinel powders synthesized by mixed-fuel solution combustion synthesis approach

The incorporation of yttrium ions into the structure of magnesium aluminate spinel can be an effective approach to modify its microstructure, enhancing its formation, sintering behavior, and mechanical properties. In this work, a mixed-fuel solution combustion synthesis approach was used to prepare yttrium-doped spinel powders with the composition MgAl2-xYxO4 (x=0; 0.02; 0.06 and 0.10). It was shown that combustion of magnesium-, aluminum- and yttrium-nitrate salts solution in the presence of a mixture of specific fuels for each metal nitrate enables the direct production of crystalline spinels without the need for additional thermal treatment. Structural and morphological characterization showed that the main phase in all samples is a spinel phase (S.G. Fd3-m), while periclase (MgO), monoclinic yttrium aluminate (Y4Al2O9), and yttrium aluminum garnet (Y3Al5O12) were found in small portion in some samples. The average crystallite size increased in Y3+-substituted samples relative to undoped MgAl2O4, from 15 nm up to 40 nm. The lattice parameter increased with increase in yttrium content, ranging from 8.071 ? to 8.086 ?. The specific surface area of the synthesized powders spans from 8.2 m?/g for the undoped powder to 3.3 m?/g for the Y3+- substituted spinels with the maximum added yttrium content.