ペロブスカイト型酸化物Sr_2(Sr_<1-x>M_x)TaO_z(M=Ca, Nd)の合成と格子歪み

概要

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The perovskite-type solid solutions Sr_2(Sr_<1-x>M_x)TaO_z(M=Ca, Nd) were synthesized. Lattice distortion and cation ordering in the octahedral site of the perovskite type structure were investigated using Rietveld analysis of powder X-ray diffraction data. Cubic perovskite-type phases with cation ordering in octahedral site were obtained for Sr_2(Sr_<1-x>Ca_x)TaO_<5.5> (x=0-1), and Sr_2(Sr_<0.9>Nd_<0.1>)TaO_<5.55>. Two types of monoclinic perovskite-type phases were obtained for Sr_2(Sr_<1-x>Nd_x)TaO_z. The unit cell of the solid solutions for x=0.3-0.7 was close to a tetragonal cell. The distortion of the solid solutions was due to tilting octahedra and a difference in the direction of tilt was observed between the compounds for x=0.3-0.7 and x=0.9-1.0. Degree of monoclinic distortion increased with increasing Nd^<3+> content. Cation ordering in the octahedral sites was observed in all the compositions investigated for Sr_2(Sr_<1-x>Nd_x)TaO_z. Increase of Nd^<3+> content possibly causes increase of oxygen content z. The present results suggest that increase of oxygen content is one of the reasons to cause the lattice distortion for Sr_2(Sr_<1-x>M_x)TaO_z(M=Ca, Nd).
社団法人日本セラミックス協会の論文
1999-07-01