The Near-infrared Absorption Spectra of Lanthanide Chlorides Dissolved in Molten LiCl–NaCl–KCl Eutectic

Abstract

Abstract Using a high temperature cell for molten salts, a spectrophotometric investigation in the near-infrated region form 0.8 to 2.6 μ and at temperatures from 400 to 800°C has been carried out with fourteen lanthanide chlorides dissolved in a LiCl–Nacl–KCl mixture of eutectic composition (49.0-17.3-33.7 mol%, m.p. 333°C. Praseodymium, neodymium, samarium, dysprosium, holmium, erbium, thulium and ytterbium have characteristic absorption bands in this region. Most of the near-infrated absorption bands of lanthanide chlorocomplexes have been compared to similar spectra obtained in molten nitrate media. However the several absorption bands have been found to be different in molten nitrate and chloride eutectics. Thus, the absorption bands of europium and terbium have been observed in nitrate, wheras their bands have not been found in chloride, and the absporption bands of praseodymium, samarium and holuium beyond the 1.4 μ range have been found to be located at different wavelengths. these solvent, for the ligand field affects the 4f-electronic energy levels of the above elements. The absorption peaks of lanthanide ions decrease as the teperature increases, partly due to the change in the concetration of the ions associated with the volume change. However, all the characteristic absorption bands of lanthanide in the near-infrared region have stable molar absorptivities at a constant temperature. These absorption bands can be used for the investigation of chemical constitution and electronic structure, for anlysis and for other purposes.