Protons in perovskite nitrides and oxide nitrides: A first principles study of ThTaN3 and SrTaO2N

Nitrides and oxide nitrides are evaluated as a new class of proton conducting ceramics by first principles defect calculations on SrTaO2N and ThTaN3 perovskites. The level of proton incorporation is obtained from the thermodynamics of dissociative absorption of water and ammonia into anion vacancies in the acceptor doped materials. Protons are found to be significantly more stable associated with the nitride ions than the oxide ions in SrTaO2N and the proton position and bond length to the anions in both materials are mostly very similar to those in corresponding perovskite oxides such as SrZrO3. In comparison to SrZrO3, the concentration of protons is significantly lower in ThTaN3 and SrTaO2N.