838
P. Kolodziej et al. / Journal of Alloys and Compounds 480 (2009) 834–838
formed in the MX–LnX3 liquid mixtures (Ln = lanthanide, M = alkali
metal, X = Cl, Br). These ions constitute the predominant species in
the MX-rich liquid mixtures. As the LnX3 concentration increases,
distortion of octahedra, which are bridged by halide anions, takes
place. Neodymium(III) complex formation in molten NaCl, KCl,
RbCl, CsCl and (Li–K)Cleut was evidenced by electronic spectroscopy
[23]. Predominant octahedral local symmetry of Nd3+ was found
over the entire composition range including pure molten NdCl3.
of a good halide ions donor (AgX) and result in a larger positive
electrical conductivity deviations than in the NaCl–NdCl3 melts.
4. Conclusion
The AgBr–NdBr3 binary system is an eutectic system with solid
solutions; it also includes the AgNd3Br10 compound, which decom-
poses in the solid state. These results were discussed critically with
previous data from literature.
3−
The formation of these LnX6 complexes influences the electrical
conductivity and induces the appearance of the negative devia-
tion in the system NaCl–NdCl3. The mixing enthalpy measurements
performed on the MX–NdX3 liquid mixtures [24,25] (X = Cl, Br)
also suggested the existence of these octahedral complexes. This
enthalpy, negative in all systems, was found to increase (in abso-
lute value) with alkali metal cation size. Similarly, as described
above for electrical conductivity deviations, the maximum mix-
ing enthalpy (in absolute value) was situated at compositions of
about 30–40 mol% NdX3. This was ascribed to the possibility of
The specific electrical conductivity of AgBr–NdBr3 liquid mix-
tures was also determined. It was discussed in terms of NdBr6
octahedral complexes formation in the melts.
3−
Acknowledgements
Financial support by the Polish Ministry of Science and Higher
Education from budget on science in 2007–2010 under the grant
no. N204 4098 33 is gratefully acknowledged.
L.R. and I.Ch. wish to thank the Ecole Polytechnique de Marseille
for hospitality and support during this work.
3−
NdX63− complex formation. We had assumed that complex NdX6
anions dominate in melts of neodymium(III) halide with alkali
metal halides (especially for systems with heavier alkali metal
cations), although the possibility of the existence of other forms of
complex could not be excluded. These conclusions were confirmed
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3−
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ter “donor” of halide ions than NaCl. Thus in AgX-rich melts the
3−
amount of NdX6
complexes formed is larger than in NaCl-rich
mixtures. Hence larger negative deviations of electrical conductiv-
ity in the AgX–NdX3 system. In NdX3-rich mixtures a disruption of
polymeric structure takes place. It will be more marked in the case