Abstract
Lattice enthalpies ΔLH° of lanthanide orthovanadates, LnVO4 (Ln = Ce Lu, except Pm) have been determined from the Born-Haber thermochemical cycle and compared with those calculated by an empirical equation. Two different sets of enthalpies of formation of LnVO4, from oxides (Ln2O3, V2O5) and from elements, have been used but the differences in ΔLH° are small. The Born-Haber cycle in both routes yields close values of ΔLH° to those obtained after an empirical equation proposed by Glasser and Jenkins. It has been found that the partial derivative of the lattice enthalpies to the molar volumes corresponds by magnitude and dimension to the shear moduli of these crystals. (doi: 10.5562/cca2298)
Highlights
Lanthanide orthovanadates, LnVO4 (Ln = Ce - Lu) exhibit valuable catalytic, electric, magnetic and optical properties
The thermodynamic assessment of lanthanide orthovanadates is incomplete, e.g. five different sets exist in the changes of the standard enthalpy (CSE) of formation with values varying about 50 kJ mol–1 for SmVO4.13,14 In Ref. 13, CSE of formation of LnVO4 (Ln = Ce - Lu, except Pm, Yb) from oxides and from elements have been determined at T = 298.15 K and at T = 1075 K in solvent of lead borate (2PbO×2B2O3)
The values of the CSE of LnVO4 lattice determined by the Born-Haber thermochemical cycle vary in a narrow range, about 1.1–1.4 % within the lanthanide series to the mean value, respectively for those determined from CSE of formation of LnVO4 from oxides or from elements
Summary
Lanthanide orthovanadates, LnVO4 (Ln = Ce - Lu) exhibit valuable catalytic, electric, magnetic and optical properties. The thermodynamic assessment of lanthanide orthovanadates is incomplete, e.g. five different sets exist in the changes of the standard enthalpy (CSE) of formation with values varying about 50 kJ mol–1 for SmVO4.13,14 In Ref. 13, CSE of formation of LnVO4 (Ln = Ce - Lu, except Pm, Yb) from oxides and from elements have been determined at T = 298.15 K and at T = 1075 K in solvent of lead borate (2PbO×2B2O3). The single prime (I) indicates different bond length with the cluster LnO8I compared to LnO8
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