Ferroelectric properties, narrow band gap and ultra-large reversible entropy change in a novel nonlinear ionic chromium(vi) compound

Abstract

A novel chromium(VI)-based compound, [(CH₃CH₂)₃N(CH₂Cl)][CrO₃Cl] (1), undergoes a high-temperature phase transition at around 340.9 K, accompanied by an ultra-large entropy change of 63.49 J mol⁻¹ K⁻¹. Compound 1 exhibits a moderate ferroelectric polarization of 0.48 μC cm⁻² and a remarkable CD signal. Strikingly, 1 occupies a narrow band gap of 2.22 eV, which is chiefly attributed to the inorganic [CrO₃Cl]⁻ tetrahedron. It is believed that these findings will contribute to an alternative pathway for the design of multifunctional ferroelectric materials, whose potential applications will be in semiconductors, energy storage, etc.