酸素欠損ペロブスカイトSr_<2-x>La_xMg_<1-y>Ta_<1+y>O_zにおける陽イオンの規則配列

概要

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Perovskite-type solid solutions, Sr_<2-x>La_xMg_<1-y>Ta_<1+Y>O_z, were synthesized and cation ordering between Mg^<2+> and Ta^<5+> in the solid solutions was investigated. In the Sr_<2-x>La_xMgTaO_z system, the(NH_4)_3FeF_6-type(1:1 order)phase was formed in the compositional range, x≥0.4. However, few degree of the cation ordering between Mg^<2+> and Ta^<5+> was also observed in the solid solutions, 0≤x≤0.3. These results suggest that the cation ordering between Mg^<2+> and Ta^<5+> in Sr_<2-x>La_xMgTaO_z system is affected by the average charge of A-site cation or, in other words, by the oxygen content. The 1:2-type ordering was observed in the Sr_<2-x>La_xMg_<1-y>Ta_<1+y>O_z solid solutions, x=0 for y≥0.3, and x≤0.1 for y=0.1, 0.2. In particular, the disappearance of the 1:2 ordering due to small amount of La^<3+> substitution was observed in the stoichiometric Sr_2Mg_<0.67>Ta_<1.33>O_6-LaSrMgTaO_6 solid solution. However, in the case of the composition containing oxygen vacancy, the 1:2 ordered phase was formed at the composition Mg/Ta=0.8/1.2 and 0.9/1.1, although they have 20% and 35% higher Mg^<2+> content than in the case of Mg/Ta=1/2, respectively. These results suggest that the 1:2 ordered structure is stabilized by the presence of oxygen vacancy.
社団法人日本セラミックス協会の論文
1999-03-01