Homochiral Nickel Nitrite ABX₃ (X = NO₂^-) Perovskite Ferroelectrics

Chiral organic-inorganic perovskites (COIPs) have recently attracted increasing interest due to their unique inherent chirality and potential applications in next-generation optoelectronic and spintronic devices. However, COIP ferroelectrics are very sparse. In this work, for the first time, we present the nickel-nitrite ABX₃ COIP ferroelectrics, [(R and S)-N-fluoromethyl-3-quinuclidinol]Ni(NO₂)₃ ([(R and S)-FMQ]Ni(NO₂)₃), where the X-site is the rarely seen NO₂^- bridging ligand. [(R and S)-FMQ]Ni(NO₂)₃ display mirror-relationship in the crystal structure and vibrational circular dichroism signal. It is emphasized that [(R and S)-FMQ]Ni(NO₂)₃ show splendid ferroelectricity with both an extremely high phase-transition point of 405 K and a spontaneous polarization of 12 μC/cm². To our knowledge, [(R and S)-FMQ]Ni(NO₂)₃ are the first examples of nickel-nitrite based COIP ferroelectrics. This finding expands the COIP family and throws light on exploration of high-performance COIP ferroelectrics.