| Abstract Scope |
Compositionally complex rare-earth aluminum-based garnets, A<sub>3</sub>B<sub>5</sub>O<sub>12</sub>, with up to five equimolar rare-earth elements on the A site, are being investigated for refractory properties. Taking into account the ionic radii of tri-valent rare-earth elements, Yb<sup>3+</sup>, Gd<sup>3+</sup>, Dy<sup>3+</sup>, and Ho<sup>3+</sup> were selected, with a less than 4% difference in ionic radius compared to Y<sup>3+</sup>. Two, three, four, and five equimolar combinations were synthesized using solid-state techniques. When fired at 1650 <sup>o</sup>C powder X-ray diffraction data show that (Y<sub>0.5</sub>Yb<sub>0.5</sub>)<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> and (Y<sub>0.33</sub>Yb<sub>0.33</sub>Gd<sub>0.33</sub>)<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> are the single-phase garnet (Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>) structure. However, target combinations of (Y<sub>0.25</sub>Yb<sub>0.25</sub>Gd<sub>0.25</sub>Dy<sub>0.25</sub>)<sub>3</sub>Al<sub>5</sub>O<sub>12</sub> and (Y<sub>0.20</sub>Yb<sub>0.20</sub>Gd<sub>0.20</sub>Dy<sub>0.20</sub>Ho<sub>0.20</sub>)<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>, are multiphase, with the garnet structure as the predominate phase and less than 10 wt% of the perovskite (ABO<sub>3</sub>) structure present as a secondary phase. Wet chemistry synthesis techniques will be implemented to compare to the solid-state synthesis and high-temperature X-ray diffraction, complemented by TGA analysis, will explore the reaction pathways. |