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

Oxygen‐deficient BaAl 2 O 4 , with strong optical absorption in the spectra range from 200 to 2500 nm, was prepared by a simple and economic thermal treatment of BaAl 2 O 4 in a H 2 gas flow. Further studies found that a molar ratio of oxygen vacancies of about 0.4 % existed in the prepared oxygen‐deficient BaAl 2 O 4 sample. The influence of oxygen vacancies on the electronic band structures and optical absorption of BaAl 2 O 4 are elucidated via first principle calculations. Oxygen vacancies introduce impurity states above the valence band; these impurities expand and enhance the optical absorption of BaAl 2 O 4 . This approach is proposed to develop a new type of optical materials and to be applicable to many wide bandgap materials.