A-Site Ordered Double Perovskite CaMnTi₂O₆ as a Multifunctional Piezoelectric and Ferroelectric-Photovoltaic Material

The double perovskite CaMnTi₂O₆, is a rare A-site ordered perovskite oxide that exhibits a sizable ferroelectric polarization and relatively high Curie temperature. Using first-principles calculations combined with detailed symmetry analyses, we identify the origin of the ferroelectricity in CaMnTi₂O₆. We further explore the material properties of CaMnTi₂O₆, including its ferroelectric polarization, dielectric and piezoelectric responses, magnetic order, electronic structure, and optical absorption coefficient. It is found that CaMnTi₂O₆ exhibits room-temperature-stable ferroelectricity and moderate piezoelectric responses. Moreover, CaMnTi₂O₆ is predicted to have a semiconducting energy band gap similar to that of BiFeO₃, and its band gap can further be tuned via distortions of the planar Mn-O bond lengths. CaMnTi₂O₆ exemplifies a new class of single-phase semiconducting ferroelectric perovskites for potential applications in ferroelectric photovoltaic solar cells.