Alkaline Earth Metal-Based Hybrid Organic-Inorganic Perovskite-Like Ferroelectrics.

Hybrid organic-inorganic perovskites (HOIPs) with the ABX formula have garnered significant scientific interest owing to their substantial technological promise in photovoltaics, optoelectronics and ferroelectrics. Their structural diversity and molecular-scale chemical programmability provide an exceptional platform for engineering diverse functional HOIP architectures through targeted compositional design. However, the strategic potential of alkaline earth metals (e.g., Ca, Sr, and Ba) in HOIP assembly remains largely unexplored, with ferroelectric implementations yet to be realized, despite their historical roots in perovskite evolution dating back to the eponymous CaTiO mineral discovered in 1839. Here, for the first time, we report a new family of alkaline earth metal-based HOIP-like ferroelectrics. Benefiting from three-dimensional cage-like structure and multiaxial characteristics, (pyrrolidinium)Ba(ClO) as a representative shows pronounced ferroelectricity with robust polarization switching in both bulk single crystals and compressed polycrystalline powder pellets. Molecular fluorination strategy on pyrrolidinium cation further optimizes the comprehensive ferroelectric properties (R-3-fluoropyrrolidinium)Ba(ClO), enhancing Curie temperature, increasing polar axes and doubling polarization values. Combined with their easy preparation and good plasticity, this discovery provides a brand-new structural paradigm for HOIP ferroelectrics and highlights exceptional promise in emerging flexible ferroelectric applications.