The samples contained undesired B2O2Se between 6.2-12.8 wt% and partially unreacted binary phases with up to 59.0 wt%, making them unusable for further analysis. As the experimental conditions for the spinel syntheses were identical, the higher content of oxide species compared to the Sc-based spinel might possibly be explained by a higher purity of the Sc powder, even if metal precursors with the same purity were purchased. To still obtain the new spinels in high purity, nevertheless, we carried out a two-step synthesis, using metal chips with less surface area and therefore probably less oxide impurity than the corresponding metal powder precursors. The XRD patterns of the first step of the synthesis (Figure ), the formation of the binary selenides, indicate B2Se3 compounds with a comparable high purity to Sc2Se3 and MgSe prepared from precursor powders. Thus, the binary selenides were found to be suitable reactants for synthesizing the corresponding spinels in a subsequent reaction step.