Sc_2(MoO_4)_3の異方性熱膨張と相転移

概要

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Lattice deformation in monoclinic Sc_2(MoO_4)_3, induced by both thermal expansion and phase transition, has been investigated by a matrix algebra analysis. From 4 K to 178 K, one of the principal distortions of the monoclinic lattice (λ_1) invariably showed a positive coefficient of thermal expansion, while the other two distortions λ_2 and λ_3 showed nagative thermal expansion in the temperature region of T<55K (λ_2) and T<35K (λ_3). Because of the bidimensional shrinkage along the latter two axes, volumetric contraction occurred below 30 K. The λ_2-axis coincides with the crystallographic b-axis. The intersection angle between the λ_1-axis and the crystallographic c-axis was 〜78.8° at 11 K, and it steadily decreased to 〜20.1° with in-creasing temperature up to 178 K. The magnitude of lattice deformation nearly along [3^^-02^^-] is negligibly small. Therefore, the lattice deformation induced by the monoclinic-to-orthorhombic phase transition at 178 K was accompanied essentially by bidimensional expansion along [010] and nearly along [2^^-05^^-], the magnitudes of which are, respectively, 〜0.6 and 〜0.9%.
社団法人日本セラミックス協会の論文
2001-10-01