Abstract
AbstractProblems of the dipole ordering and ionic conductivity of Na_3Sc_2(PO_4)_3 polycrystal that has three polymorphic phases—α, β, and γ—are studied. The features of the α-Na_3Sc_2(PO_4)_3 crystal structure and the dipole ordering and relaxation polarization in the α and β phases are specified. The origin of the dipole ordering in the α phase and the partial dipole disordering in the β-Na_3Sc_2(PO_4)_3, as well as the high ionic conductivity in the β and γ phases of the Na_3Sc_2(PO_4)_3 polycrystal are associated with phase transformations α → β, β → γ that result in structural changes of the rhombohedral {[Sc_2(PO_4)_3]^3–}_3∞ crystalline framework. A model explaining the emergence of the dipole ordering and the ionic conductivity phenomena in Na_3Sc_2(PO_4) is proposed.