Preparation of Bulk‐Phase Nitride Perovskite LaReN₃ and Topotactic Reduction to LaNiO₂‐Type LaReN₂

Abstract

While halide and oxide perovskites are numerous and many display outstanding properties, ABN3 perovskite nitrides are extremely rare due to synthetic challenges arising from the low chemical potential of nitrogen and a tendency to form low‐coordination nitridometallate anions. We report the preparation of a perovskite nitride LaReN3 through azide‐mediated oxidation at high pressure. High‐resolution synchrotron diffraction shows that LaReN3 has a low‐symmetry, triclinic, perovskite superstructure resulting from orbital ordering with strong spin‐orbit coupling distortions. Topotactic reduction of LaReN3 above 500 °C leads to layered tetragonal LaReN2 via a probable LaReN2.5 intermediate, which is the first reported example of nitride defect perovskites. Magnetisation and conductivity measurements indicate that LaReN3 and LaReN2 are both metallic solids. The two chemical approaches presented are expected to lead to new classes of ABN3 and defect ABN3−x nitride perovskite materials.

Can Nitride Perovskites Provide the Same Superior Optoelectronic Properties as Lead Halide Perovskites?

“…When anions in the oxidation state of −3 are incorporated into the perovskite structure to form pnictide perovskites, the collective oxidation state of the A and B cations is as large as +9. This seems to imply a larger flexibility in cation combinations, but most of the combinations must be ruled out based on the prerequisite for the stable pnictide perovskites that the A and B cations have to exhibit high formal charges, e.g., A 3+ B 6+ and A 4+ B 5+ , while also satisfying the Goldschmidt tolerance factor. , Pnictide perovskites are extremely rare due to the long-standing synthetic challenge. Among pnictide perovskites, only a few nitride perovskites (N 3– is the smallest pnictogen anion) have been synthesized.…”