VIBRATIONAL BEHAVIOR OF GUEST ANIONS IN THE LI3ASO4 STRUCTURE

Citation
R. Cloots et al., VIBRATIONAL BEHAVIOR OF GUEST ANIONS IN THE LI3ASO4 STRUCTURE, Journal of solid state chemistry, 115(1), 1995, pp. 83-87
Citations number
10
Categorie Soggetti
Chemistry Inorganic & Nuclear","Chemistry Physical
ISSN journal
00224596
Volume
115
Issue
1
Year of publication
1995
Pages
83 - 87
Database
ISI
SICI code
0022-4596(1995)115:1<83:VBOGAI>2.0.ZU;2-Z
Abstract
We have investigated the vibrational behavior of the v(3) mode of gues t anions ((PO4)(3-), (SO4)(2-)) forming a dilute solid solution with t he two polymorphic species of Li3AsO4. For the (PO4)(3-)anion, the v(3 ) mode is represented by a more or less resolved triplet, as expected from the low site symmetry and the small distortion of the host anion. But a much more complex vibrational behavior is exhibited by the (SO4 )(2-) anion, whose different charge must be chemically compensated for , either by a Li+ vacancy, or by another suitable anion such as (SiO4) (4-). Compensation by a vacancy leads to a large splitting of the trip let components, suggesting a close association between the (SO4)(2-) a nion and the vacancy; the multiplet observed for the HT polymorph is j ustified by the existence of two structurally different types of vacan cies. Charge compensation by the (SiO4)(4-) ion leads to a complex spe ctrum indicating the existence of two types of structurally different (SO4)2- anions, in relation to two structurally different mechanisms o f charge compensation. (C) 1995 Academic Press, Inc.