Crystal Structures and Phase Transitions in A-Site Deficient Perovskites Ln1/3TaO3

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• 作者：Qingdi Zhou ; Paul J. Saines ; Neeraj Sharma ; Jimmy Ting ; Brendan J. KennedyZhaoming ZhangRay L. WithersKia S. Wallwork
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：November 11, 2008
• 年：2008
• 卷：20
• 期：21
• 页码：6666-6676
• 全文大小：466K
• 年卷期：v.20,no.21(November 11, 2008)
• ISSN：1520-5002

文摘

The synthesis and structures of the perovskites Ln_1/3TaO₃ are described. As the size of the Ln cation is reduced, the compounds display a sequence of structure: P4/mmm/La → Cmmm/Ce−Gd → Pmma/Tb, Dy → Pmc2₁/Ho, Er. Although apparently tetragonal in P4/mmm, electron diffraction patterns of Tm_1/3TaO₃ reveal this has a complex incommensurate structure. Likewise Gd_1/3TaO₃ appears metrically tetragonal, but electron diffraction and synchrotron X-ray powder diffraction demonstrate this is actually orthorhombic. The suppression of the spontaneous orthorhombic strain in Gd_1/3TaO₃ is thought to be due to the proximity to the first-order Cmmm−Pmma transition. Variable temperature studies show both Tb_1/3TaO₃ and Dy_1/3TaO₃ undergo a first-order Cmmm−Pmma transition upon heating.