While many functional ceramics are either oxides, chalcogenides or halides, the mixed-anion compounds have drawn attention as new types of inorganic material. Because of unique coordination, crystal structures and tunability of energy of valence band top in such compounds, it is possible that fundamentally different, innovative functions may be created. Materials with such innovative functions are expected by using several different anions with differing electronegativity and polarizability, and exploiting exceptional ability of such anions to control chemical bonding and electronic structures. Many elements that become anions have a high Clarke number, and mixed-anion compounds have the possibility of becoming materials that act as a driving force for element strategies.
In this talk, some examples of development of new phosphor materials will be introduced by giving asymmetric ligand field to rare-earths and achieving lower excitation energy of charge transfer band by the valence band engineering in oxynitride and oxyhydride systems.