Structural Modifications Induced by Composition in the La1.33-xNa3xTi2O6 Perovskites: A

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• 作者：Ana I. Ruiz ; M. Luisa L&oacute ; pez ; Carlos Pico ; and M. Luisa Veiga
• 刊名：Chemistry of Materials
• 出版年：2005
• 出版时间：March 22, 2005
• 年：2005
• 卷：17
• 期：6
• 页码：1391 - 1397
• 全文大小：481K
• 年卷期：v.17,no.6(March 22, 2005)
• ISSN：1520-5002

文摘

Polycrystalline samples of general composition La_1.33-xNa_3xTi₂O₆ were prepared by the "liquid mix"technique. The structural analysis carried out from different techniques (XRPD, ED, HREM, and NPD)evidences that these perovskites undergo phase transformations that seem to be mainly related to thenumber of A-vacancies. For high degrees of substitution, x, that imply low number of vacant A-sites, arandom distribution of Na⁺ and La³⁺ ions in these sites is observed. When this number increases (for x= 0.16 and 0.11) two different cells are adopted, in which the A-cations are ordered by layers along onedirection, whose dimensions are a ges/entities/ap.gif"> b ges/entities/ap.gif"> ges/entities/radic.gif">2a_p; c ges/entities/ap.gif"> 2a_p (space group Pbmm) and a ges/entities/ap.gif"> b ges/entities/ap.gif"> c ges/entities/ap.gif"> 2a_p(space group Cmmm), respectively. These structural changes are analyzed on the basis of the group-subgroup relations and the tilting of the TiO₆ octahedra.