Discovery of an Antiperovskite Ferroelectric in [(CH 3 ) 3 NH] 3 (MnBr 3 )(MnBr 4 ).

It is known that perovskites with the general chemical formula of ABX3 (A, B = cations, X = anion) have been intensively studied over the last half century because of their diverse functional properties, such as ferroelectricity in BaTiO3 , piezoelectricity in PZT (lead zirconate titanate), and recently developed photovoltaic properties in CH3 NH3 PbI3 . However, rather less attention has been paid to their "inverse" analogs, antiperovskites, which have a chemical formula X3 BA, where A and B are anions and X is a cation. Although most of important ferroelectrics are perovskites, no antiperovskite ferroelectrics have been found since the discovery of antiperovskites in 1930. Here, for the first time, we report a X3 BA antiperovskite ferroelectric [(CH3 )3 NH]3 (MnBr3 )(MnBr4 ) (where (CH3 )3 NH is X, MnBr3 is B, and MnBr4 is A), which shows outstanding ferroelectricity with a significantly high phase transition temperature of 458 K as well as fascinating photoluminescence properties with two intense emissions. This finding opens a new avenue to explore the golden area of antiperovskites for high-performance functional materials.