The rare-earth aluminate garnets RE3Al5O12 (RE = Eu -Lu, Y) are attractive host materials for optical applications in solid state lasers, 1 lighting and display technologies 2 and scintillation detectors , owing to their excellent optical isotropy, chemical and physical stability, and their crystal structure exhibiting three types of cationic environments suitable for doping with different emission centres. These materials form over extremely narrow compositional ranges, typically represented as line phases in the RE2O3 -Al2O3 pseudo-binary phase equilibria diagrams. This characteristic is rooted in their crystal chemistry: their structures (general formula A3B2C3O12) feature three cation sublattices A (8-coordinate dodecahedral site), B (6-coordinate octahedral) and C (4-coordinate tetrahedral), shown in Figure .