HREM studies of intergrowths in Sr₂[Sr_n − 1Ti_nO_3n + 1] Ruddlesden–Popper phases synthesized by mechanochemical activation

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• 作者：Teresa Hungria ; Ian MacLaren ; Hartmut Fuess ; Jean Galy ; Alicia Castro
• 关键词：Perovskites ; Crystal structure ; Electron microscopy
• 刊名：Materials Letters
• 出版年：2008
• 期刊代码：59_0167577x
• 类别：ms
• 出版时间：30 June 2008
• 卷：62
• 期：17-18
• 页码：3095-3098
• 文件大小：478 K

摘要

A mechanochemical activation route has been applied in order to obtain the n = 1–4 and ∞ members of the Sr₂[Sr_{n − 1}Ti_nO_{3n + 1}] Ruddlesden–Popper series from different (n + 1)SrO:nTiO₂ mixtures. The mechanosynthesis of SrTiO₃ and Sr₂TiO₄ was observed during the milling process from the initial stoichiometric mixture, but in the cases of the n = 2–4 members, a subsequent thermal treatment was needed. The synthesis protocol of Sr₃Ti₂O₇ has been greatly improved and this compound can be isolated as a single, crystalline phase after annealing at 800 °C. In the case of Sr₄Ti₃O₁₀ and Sr₅Ti₄O₁₃, the formation temperature was also decreased, but members with n = 3 and 4 could not be isolated. Detailed investigations using electron microscopy methods (TEM, HREM and SAED) were carried out in the samples corresponding to n = 2–4. Although a single ordered Sr₃Ti₂O₇ structure is dominant in the sample corresponding to n = 2, a few intergrowths of other Ruddlesden–Popper phases were observed. In the cases of n = 3 and 4, the intergrowths of Ruddlesden–Popper phases are more frequent than in the n = 2 composition and are randomly distributed in the sample. The more frequent occurrence of such stacking faults, with increasing n value, leads to a somewhat disordered layer stacking sequence.