High-Pressure Synthesis, Crystal Structure, Chemical Bonding, and Ferroelectricity of LiNbO <sub/>3</sub> -Type LiSbO <sub/>3</sub>

摘要： A polar LiNbO3 (LN)-type oxide LiSbO3 was synthesized by a high-temperature heat treatment under a pressure of 7.7 GPa and found to exhibit ferroelectricity. The crystal structural re?nement using the data of synchrotron powder X-ray di?raction and neutron di?raction and the electronic structure calculation of LN-type LiSbO3 suggest a covalent-bonding character between Sb and O. When comparing the distortion of BO6 in LN-type ABO3, the distortions of SbO6 in LiSbO3 and SnO6 in ZnSnO3, which included a B cation with a d10 electronic con?guration, were smaller than those of BO6 in LN-type oxides having the second-order Jahn?Teller active B cation, e.g., LiNbO3 and ZnTiO3. The temperature dependence of the lattice parameters, second harmonic generation, dielectric permittivity, and di?erential scanning calorimetry made it clear that a second-order ferroelectric?paraelectric phase transition occurs at a Curie temperature of Tc = 605 ± 10 K in LN-type LiSbO3. Further, ?rst-principles density functional theory calculation suggested that perovskite-type LiSbO3 is less stable than LN-type LiSbO3 under even high pressure, and the ambient phase of LiSbO3 directly transforms to LN-type LiSbO3 under high pressure. The phase stability of LN-type LiSbO3 and the polar and ferroelectric properties are rationalized by the covalent bonding of Sb?O and the relatively weak Coulomb repulsion between Li+ and Sb5+.