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Irreversible Electron-Induced Structural Change during HREM Imaging in Lithium Ruddlesden–Popper Phases in the Series Li2Lax (Nb2n−3xTi3x−n)O3n+1 (n=2, 3, 4) and Li2Sr1.5(Nb3−xFex)O10−x

1999; Elsevier BV; Volume: 145; Issue: 1 Linguagem: Inglês

10.1006/jssc.1999.8232

1095-726X

Marie‐Pierre Crosnier‐Lopez, Nattamai S. P. Bhuvanesh, H. Duroy, J.L. Fourquet,

Microwave Dielectric Ceramics Synthesis

Several lithium Ruddlesden–Popper compounds are investigated by TEM (ED and HREM) in the series Li2Lax (Nb2n−3xTi3x−n)O3n+1 (n=2, 3, and 4, for x=0.833, 1.78, and 2.25, respectively) and Li2Sr1.5 (Nb3−xFex) O10−x (for n=3; x=0 and 0.115). These studies confirm the crystal structures previously established from single crystal X-ray diffraction data: they consist of perovskite layers separated by Li+ ions in distorted tetrahedral coordination. After the HREM study, for all the examined compounds, an irreversible structural change is evidenced leading to a unique model (space group I4/mmm) characterized by the preservation of the perovskite layers and by a substantial shrinking of the c parameter ( perpendicular to the perovskite slabs). In the hypothesis of the conservation of the cells contents, this phenomenon is explained by a concomitant change in the Li+ coordination which becomes octahedral.