Kazuko Fukushima

X-ray diffraction and Raman spectroscopic study on the short-range structure of molten CeCl3

Abstract The short-range structure of molten CeCl 3 at 1143 K was studied by means of X-ray diffraction and Raman spectroscopy, and the octahedral configuration of CeCl 6 3− was found to exist in molten CeCl 3 . Also discussed is the medium-range structure with some assumptions.

Raman spectroscopic study of molten SmCl3–ACl systems (A=Li, Na, K)

Abstract Raman spectra of molten SmCl 3 –ACl systems (A=Li, Na, K) were measured at different compositions and temperatures. The spectra showed polarized peaks centered at about 256 cm −1 in the whole range of concentration and depolarized peaks at about 120 cm −1 in the low concentration range of SmCl 3 . These Raman shifts were identified as the totally symmetric stretching vibration υ 1 and the degenerate bending vibration υ 5 of octahedral SmCl 6 3− complex anion, respectively. Peak splitting of the isotropic component was recognized clearly in the reduced Raman spectra of mixtures. Clustering of complex anions is thought to occur in the melts. However, the clustering might be restrained when the SmCl 3 concentration became relatively low by adding LiCl, NaCl or KCl. The υ 5 peak was the strongest at the SmCl 3 concentration of 25 mol% in the SmCl 3 –KCl system among the three systems. The temperature effect on the Raman shift, reflecting the structural change, was negligibly small between 823 K and 1023 K.

Short range structure of B2O3–Cs2O glasses analyzed by x‐ray diffraction and Raman spectroscopy

Structural analyses of pure B2O3, B2O3(90 mol%)–Cs2O (10 mol%) and B2O3 (80 mol%)–Cs2O (20 mol%) glasses were made by an x‐ray diffraction method and the effects of Cs2O addition were investigated on the short range structure of the glasses. Furthermore, Raman spectroscopic studies were applied to analyze the interatomic interactions between boron and oxygen atoms. Due to x‐ray diffraction, pure B2O3 was confirmed to have BO3 triangles which formed the so‐called boroxol ring structure. When Cs2O was added to B2O3, the boroxol ring structure still remained but some parts of BO3 triangles was definitely converted to BO4 tetrahedra. This result was also supported by Raman spectroscopic observations. The other important consequences were that a Cs atom was surrounded by six O atoms, and four Cs–O interatomic distances were about 3 A but two pairs 3.5 A, indicating that the distorted Cs–O octahedra might exist in the B2O3–Cs2O glasses. This spatial arrangement of Cs and O atoms was quite different from the cor...

Molar volume variation and ionic conduction in molten ErCl3NaCl and ErCl3KCl systems

Molar conductivities (Λ) of molten ErCl3NaCl and ErCl3KCl systems were evaluated using the data of molar volume, Vm, and conductivity, ϰ, which were measured as a function of the mole fraction of ErCl3 and temperature, by dilatometry and a conventional a.c. technique, respectively. The Λ values of molten ErCl3 were smaller than those of molten YCl3, in which a loose disordered network of edge-sharing octahedral units has been reported to exist. The Λ values of ErCl3NaCl and ErCl3KCl systems increased with decreasing ErCl3 concentration, x, and in the range x >4 0.25 the increment in Λ with x was much smaller than that in the range of x < 0.25. In a series of molten rare earth chlorides, Λ values have been found to be affected qualitatively by cationic radii and the types of linkage, that is, corner- or edge-sharing of octahedral units.

Refractive indexes and electronic polarizabilities of molten HoCl3–NaCl and HoCl3–KCl mixtures

Abstract The refractive indexes of molten HoCl 3 –NaCl and HoCl 3 –KCl mixtures were measured by goniometry using visible light at eight wavelengths and expressed as functions of both temperature and wavelength into empirical formulas by a least-squares method. The electronic polarizabilities of ions in the mixture melts were obtained from the data of refractive indexes and molar volumes, and the polarizability of a Ho 3+ ion was evaluated to be about 0.98×10 −30 m 3 according to the Clausius–Mossotti equation. The isotherms of these properties show little deviation from their additivity line.

Phase diagram and Raman spectroscopy of EuCl2NaCl binary mixtures

Abstract A phase diagram of the EuCl 2 NaCl system was determined by differential scanning calorimetry (DSC) and the activity coefficients of EuCl 2 and NaCl in this system were estimated under some assumptions. According to DSC measurement, it was found that there were two phase transitions at 1123.9 K and 1016.8 K. In order to specify the melting point of EuCl 2 we did Raman spectroscopy experiments. Thus, the melting point of EuCl 2 was evaluated to be 1016.8 K which was detected as the lower peak in the DSC curve. Raman spectroscopy of this system suggested that complex species were not formed clearly in the EuCl 2 poor system and the estimated activity coefficients of EuCl 2 also supported this suggestion.

XAFS study of molten zinc dibromide

Abstract The local structure of molten ZnBr 2 was investigated by X-ray absorption fine structure measurements for both Zn and Br above their K-absorption edges at 723 K. The results show that a tetrahedral coordination (ZnBr 4 ) 2− exists and most coordinates connect with the next ones through the Br − ion. The two XAFS functions k 3 χ ( k ) in the molten ZnBr 2 were reproduced by a combination of a molecular dynamics simulation and an ab initio mutiple scattering calculation of X-ray absorption spectrum.

Molar volume variation and ionic conduction in molten SmCl3NaCl, SmCl3KCl and SmCl3CaCl2 systems

Abstract Molar volume, V m , and electrical conductivity, κ, of molten SmCl 3 NaCl. SmCl 3 KCl and SmCl 3 CaCl 2 systems were measured by dilatometry and a conventional a.c. technique, respectively. The molar conductivities ( A ) were evaluated using the data of molar volume and conductivity. The A values of molten mixtures of SmCl 3 with NaCl. KCl or CaCl 2 suggested that the existence of dimeric or more polymeric complex anions might be presumed in the melt as was the case in a series of molten rare earth chlorides. Additionally, the A values of molten rare earth chlorides appeared to be affected qualitatively by the cationic radii and the types of linkage, that is, corner- or edge-sharing of octahedral units in melts. The A values of molten SmCl 3 NaCl and SmCl 3 KCl systems increased with decreasing SmCl 3 concentration, x , and in the range of x > 0.25 the increment in A to x was much smaller than that in the range of x 3 CaCl 2 system, the A values increased almost linearly with decreasing SmCl 3 concentration all over the range.

Electronic polarizabilities of Sr2+ and Ba2+ estimated from refractive indexes and molar volumes of molten SrCl2 and BaCl2

Abstract The refractive index and molar volume of each molten chloride were measured by goniometry and dilatometry, respectively. The refractive indexes were represented as polynomial functions of both temperature and wavelength in empirical formulas by a least-squares method, and the molar volumes were expressed as linear functions of temperature in the same manner. The electronic polarizabilities of Sr 2+ and Ba 2+ in pure SrCl 2 and BaCl 2 melts were estimated by the Clausius–Mossotti equation to be 1.43×10 −30 and 2.61×10 −30 m 3 , respectively. The correlation between the ion electronic polarizability and the ionic radius was also examined.

Raman spectroscopic study of molten ZnBr2KBr mixtures

Abstract In this study, Raman spectra of molten ZnBr 2 KBr systems were measured at different compositions and temperatures to ensure the existence of tetrahedral ZnBr 4 2− structural units. Each spectrum was deconvoluted in terms of the Gaussian function. Two polarized peaks were identified as the totally symmetric stretching vibration mode of tetrahedral ZnBr 4 2− monomer and its dimer. The relative intensities of these peaks depended on both composition and temperature, probably reflecting the ratio of monomer to dimer in the melts. The relative intensities decreased until the ZnBr 2 composition decreased down to 25 mol.%. and were constant when the composition was less than 25 mol.%. In this work, we discuss the network structure on the basis of the relative intensities of these two peaks.