Oxidation States of Europium in the Alkaline Earth Oxide and Sulfide Phosphors

Abstract

Emission and absorption spectra of the alkaline earth sulfides activated with europium and fired in a neutral atmosphere have been re‐investigated. The emission and absorption spectra of the alkaline earth oxides, also activated with Eu, and fired in a neutral or a reducing atmosphere have been obtained. The sulfides show both band emission and band absorption, as does fired in hydrogen. The other hydrogen‐fired oxides have band absorption, except for and give either mixed band and line emission or only line emission. The nitrogen‐fired oxides, except give line emission and little, if any, selective absorption. emits a broad line spectrum for both the nitrogen‐and hydrogen‐fired samples and shows no absorption peaks. Emission and absorption spectra have been correlated with the oxidation state of the activator in the several phosphors, the line emissions being associated with the presence of and the band emissions with .