Synthesis and structural characterization of the new defect pyrochlore Nd1.68Ti2O6.52
Journal
Solid State Sciences
Journal Volume
4
Journal Issue
2
Pages
167-173
Date Issued
2002
Author(s)
Abstract
The new defect pyrochlore phase, Nd1.68Ti2O6.52, has been prepared in air at 800°C starting from precursor materials obtained via a 'liquid mix' process. It crystallizes in space group Fd3m of the cubic system with Z = 8 and a = 10.233(3) Å. Its structure was determined from a Rietveld analysis. The outstanding feature of the structure is the 7-fold oxygen coordination of the Nd atom (six 48f O atoms and one 8b O′ atom) which enables to reach a bond valence sum close to +3 for Nd. EDX analyses on many crystals picked up from different preparations have shown that the Nd content of the defect pyrochlore Nd2-x[Ti2O6]O′1-3x/2 always falls within a very narrow range. This result is in very good agreement with the theoretical composition range that can be inferred from structural considerations taking into account the 7-fold oxygen coordination of Nd as a requirement. HREM investigations and image calculations confirm the defect character of the structure. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.
Publisher
Elsevier Masson SAS
Type
journal article