Self-Activated Luminescence of M2+ Niobates and Tantalates

Among 22 compounds examined for photoluminescence, only , and the metaniobates of Mg Ca, Zn, and Cd show appreciable room temperature emission. With the exception of , all of these have the columbite structure; moreover, the only essentially nonluminescent columbite‐type compound noted was . The absorption edges of the luminescent niobates lie at shorter wavelengths than those of otherwise similar compositions. This indicates a relationship between luminescence and the separation of energy states within the Nb‐O bond, as influenced by structure.