2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 3. Gaune-Escard Intl. Symp. / Molten Salt and Ionic Liquid
| Editors: | Kongoli F, Fehrmann R, Gadzuric S, Gong W, Seddon KR, Malyshev V, Iwata S |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 151 pages |
| ISBN: | 978-1-987820-65-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Thermodynamic and Transport Properties of Lanthanide(III) Halide - Alkali Metal Halide Systems
Leszek Rycerz1; Anna Danczak1; Ida Chojnacka1; Marcelle Gaune-Escard2;1WROCLAW UNIVERSITY OF SCIENCE AND TECHNOLOGY, Wroclaw, Poland; 2AIX-MARSEILLE UNIVERSITE/POLYTECH, CNRS/IUSTI UMR7343, Marseille, France;
Type of Paper: Regular
Id Paper: 139
Topic: 13
Abstract:
Thermodynamic and transport properties of the LnX3-MX binary systems (M = Li, Na, K, Rb, Cs; Ln = lanthanide; X = halide) were measured by calorimetry, differential scanning calorimetry and capillary methods. These systems are characterized by negative enthalpies of mixing. The minimum of molar mixing enthalpy is shifted towards the alkali halide-rich composition and located in the vicinity of x(LnX3) of about 0.3-0.4. Ionic radius of the alkali metal as well as ionic radius of lanthanide and halide influence the magnitude of mixing enthalpy as well as the minimum position. Absolute value of mixing enthalpy increases with decrease of lanthanide ionic radius and decreases with increase of halide ionic radius. The dependence of interaction parameter , which represents energetic asymmetry of the melts under investigation, on composition can be undoubtedly ascribed to the formation of LnX63- octahedral complexes in the systems under investigation. The existence of these complexes is confirmed by electrical conductivity measurements of LnX3-MX liquid mixtures.
Temperatures and molar enthalpies of phase transitions of the M3LnX6 congruently melting compounds (M = K, Rb, Cs) were determined and compared. This comparison showed that M3LnX6 compounds could be divided into two groups: compounds, which are formed at higher temperatures from M2LnX5 and MX, and compounds, which are stable or metastable at ambient temperature. The heat capacities of M3LnX6 compounds were determined and fitted by equations, which provides a satisfactory representation up to the temperature of the Cp discontinuity. Electrical conductivity of solid phase of M3LnX6 compounds correlates well with their heat capacity. The specific behavior of the heat capacity and electrical conductivity dependence on temperature of solid M3LnX6 compounds is undoubtedly connected with disordering of cationic sublattice formed by alkali metal cations.