Halogen-substituted quasi-spherical tetraethylammonium cations induce reversible molecular ferroelectricity in indium-based hybrid materials

Abstract

Organic–inorganic hybrid molecular ferroelectrics have gained considerable interest due to their potential applications in data storage, sensing, and switching devices. Nevertheless, designing novel molecular ferroelectric materials remains a considerable challenge. Here, a series of quasi-spherical tetraethylammonium indium halide hybrid ferroelectrics, [(CH3CH2)3NCH2X][InBr4] (X = Me (1), Cl (2), Br (3), I (4)), were synthesized using a quasi-spherical design approach incorporating halogen substitution. By introducing halogen-substituted tetraethylammonium cations into the indium-based framework, we precisely tuned the ferroelectric properties of these materials. Comprehensive characterizations—including thermal analysis (DSC), nonlinear optical response (SHG), dielectric property evaluation, and polarization-electric field loop measurements—demonstrated that all synthesized compounds possess high-Tc phase transitions, remarkable second-order nonlinear optical effects, and stable ferroelectric performance. These findings not only advance the development of high-performance ferroelectric materials but also offer new design principles for applications in information storage and sensor technologies.