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Preparation and characterization of metastable trigonal layered MSb2O6 phases (M = Co, Ni, Cu, Zn, and Mg) and considerations on FeSb2O6Electronic supplementary information (ESI) available. See DOI: 10.1039/c6dt04859e
MSb 2 O 6 compounds (M = Mg, Co, Ni, Cu, Zn) are known in the tetragonal trirutile forms, slightly distorted monoclinically with M = Cu due to the Jahn-Teller effect. In this study, using a low-temperature exchange reaction between ilmenite-type NaSbO 3 and molten MSO 4 -KCl (or MgCl 2 -KCl) mixture...
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| Main Authors: | , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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| Summary: | MSb
2
O
6
compounds (M = Mg, Co, Ni, Cu, Zn) are known in the tetragonal trirutile forms, slightly distorted monoclinically with M = Cu due to the Jahn-Teller effect. In this study, using a low-temperature exchange reaction between ilmenite-type NaSbO
3
and molten MSO
4
-KCl (or MgCl
2
-KCl) mixtures, these five compositions were prepared for the first time as trigonal layered rosiaite (PbSb
2
O
6
)-type phases. Upon heating, they irreversibly transform to the known phases
via
amorphous intermediates, in contrast to previously studied isostructural MnSb
2
O
6
, where the stable phase is structurally related to the metastable phase. The same method was found to be applicable for preparing stable rosiaite-type CdSb
2
O
6
. The formula volumes of the new phases show an excellent correlation with the ionic radii (except for M = Cu, for which a Jahn-Teller distortion is suspected) and are 2-3% larger than those for the known forms although all coordination numbers are the same. The crystal structure of CoSb
2
O
6
was refined
via
the Rietveld method:
P
3&cmb.macr;1
m
,
a
= 5.1318(3) Å, and
c
= 4.5520(3) Å. Compounds with M = Co and Ni antiferromagnetically order at 11 and 15 K, respectively, whereas the copper compound does not show long-range magnetic order down to 1.5 K. A comparison between the magnetic behavior of the metastable and stable polymorphs was carried out. FeSb
2
O
6
could not be prepared because of the 2Fe
2+
+ Sb
5+
= 2Fe
3+
+ Sb
3+
redox reaction. This electron transfer produces an additional 5s
2
shell for Sb and results in a volume increase. A comparison of the formula volume for the stable mixture FeSbO
4
+ 0.5Sb
2
O
4
with that extrapolated for FeSb
2
O
6
predicted that the trirutile-type FeSb
2
O
6
can be stabilized at high pressures.
New forms of MSb
2
O
6
(M = Co, Ni, Cu, Zn, and Mg) have been prepared by ion exchange. |
|---|---|
| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/c6dt04859e |