EuAl 3 (BO 3 ) 4 is a promising platform for correlating defects with QIS performance. XRF showed that the material can host percentlevel inclusions of Bi on Eu sites and Mo on Al sites. The material also has three polymorphs differing only in the ordering of A, B, and B ′ layers, including the C2/c polytype, now with reported atomic positions. These polytypes can coexist within crystals, as evidenced by C2 peaks in synchrotron powder XRD data from a primarily R32 sample. The polytype domain locations, though, are only apparent through PL mapping where sharp shifts in Eu 3+ site symmetry lead to additional peaks in the 5 D 0 → 7 F 1 transition in mixed-symmetry regions. These coherent domains are present even in flux-free polycrystalline samples synthesized by energyand time-efficient microwave-assisted sintering. Notably, these microwave samples are the first XRD-confirmed, flux-free synthesis of EuAl 3 (BO 3 ) 4 .