Synthesis and Performance of BaAl₂O₄ with a Wide Spectral Range of Optical Absorption

Abstract Oxygen‐deficient BaAl₂O₄, with strong optical absorption in the spectra range from 200 to 2500 nm, was prepared by a simple and economic thermal treatment of BaAl₂O₄ in a H₂ gas flow. Further studies found that a molar ratio of oxygen vacancies of about 0.4 % existed in the prepared oxygen‐deficient BaAl₂O₄ sample. The influence of oxygen vacancies on the electronic band structures and optical absorption of BaAl₂O₄ are elucidated via first principle calculations. Oxygen vacancies introduce impurity states above the valence band; these impurities expand and enhance the optical absorption of BaAl₂O₄. This approach is proposed to develop a new type of optical materials and to be applicable to many wide bandgap materials.