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Article Dans Une Revue Journal of Solid State Chemistry Année : 2010

Second order incommensurate phase transition in 25L-Ta2O5

Résumé

A new structural state 25L-Ta2O5, obtained from sintering and annealing treatments of a Ta2O5 powder, is identified both by electron diffraction and high resolution imaging on a transmission electron microscope (TEM). According to general rules for the different L-Ta2O5 structures proposed by Grey et al. (J. Solid State Chem. 178 (2005) 3308), a structural model is derived from their crystallographic data on 19L-Ta2O5. This model yields simulated images in agreement with high resolution TEM observations of the structure oriented along its [001] zone axis, but only for a very thin crystal thickness of less than 1.2 nm. Such a limitation is shown to be due to a modulation of the structure along its [001] axis. Actually, from an analysis of a diffuse scattering and of its evolution into satellites reflections as a function of the cooling rate, a second order incommensurate phase transition can be assumed to occur in this compound. The property of single phase samples observed by TEM is also verified by X-ray powder diffraction. In a discussion about studies performed by different authors on incommensurate structures in the system Ta2O5-WO3, it is noticed that TEM results, similar to ours, indicate that phase transitions could be expected in these structures. (C) 2010 Elsevier Inc. All rights reserved.

Domaines

Matériaux

Dates et versions

hal-01067570 , version 1 (23-09-2014)

Identifiants

Citer

M. Audier, Bernard Chenevier, Hervé Roussel, A. Lintanf Salaün. Second order incommensurate phase transition in 25L-Ta2O5. Journal of Solid State Chemistry, 2010, 183 (9), pp.2068-2076. ⟨10.1016/j.jssc.2010.07.001⟩. ⟨hal-01067570⟩
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