Compositions are generally provided that include an oxyfluoride compound. In one embodiment, the oxyfluoride compound has the formula: NaCa2−xAxGeO4−zF1−yNz where A is Ba, Sr, or a mixture thereof; 0.01≦x≦0.1; 0≦y≦0.2; and 0≦z≦0.1. Methods of forming such compounds are also generally provided.