A stoichiometric combination of α-Al 2 O 3 (Alfa Aesar, 99.9%), B 2 O 3 (Fisher, 99.98%), and Eu 2 O 3 (Acros, 99.99% trace metal basis) was mixed with a mortar and pestle. 0.15-0.6 g of the mixture was then placed in a 2 mL Al 2 O 3 cylindrical crucible. This crucible was embedded in activated carbon within a larger Al 2 O 3 high-form crucible. The larger crucible was placed in thermally insulating bricks in a 1250 W microwave oven (Panasonic NN-SN736W) where the sample was heated at maximum power for 45 min. Due to limitations with the microwave oven, the samples could not continuously run for 45 min, so a 15 + 30 min cycle was used with only around 5 s between the two time segments. Once the full cycle ended, the inner crucible was immediately removed and placed on a metal plate to cool rapidly.