Exploring order–disorder structural transitions in the Li–Nb–N–O system: The new antifluorite oxynitride Li11NbN4O2

A systematic exploratory study of the Li–Nb–N–O system at low oxygen and high lithium contents has been performed. As lithium and oxygen increase, an order–disorder transition has been identified using powder neutron diffraction data between Li16Nb2N8O, which crystallizes in an antifluorite-type superstructure with cationic and anionic ordering, and Li11NbN4O2, a new antifluorite-type oxynitride that shows structural disorder. A description of the synthetic conditions required to prepare these phases and their structural characterization is presented.