F. H. Spedding

The coordination (hydration) of rare earth ions in aqueous chloride solutions from x ray diffraction. I.TbCl3,DyCl3, ErCl3,TmCl3,and LuCl3

The rare earth complex,[RE(H3O)8]3+,has been identified in concentrated (3.2−3.6 m) aqueous TbCl3,DyCl3,ErCl3,TmCl3, and LuCl3 solutions from x ray diffraction measurements. The inner sphere water coordination of rare earth ion was obtained from quantitative resolution of the radial distribution functions. In each solution the rare earth ion has eight water nearest neighbors with the average RE3−H2O distances being 2.409, 2.396, 2.369, 2.358, and 2.338A for TbCl3,DyCl3, ErCl3, TmCl3, and LuCl3,respectively. The average RE3+. . . Cl− ion pair distances are near 4.8A.

The coordination (hydration) of rare earth ions in aqueous chloride solutions from x‐ray diffraction. III. SmCl3, EuCl3, and series behavior

The inner sphere water coordination of Sm3+ and Eu3+ in concentrated (3.23 m) aqueous chloride solutions was obtained from x‐ray diffraction measurements at 25 °C. The average water coordination is 8.8 for Sm3+ and 8.3 for Eu3+. The average RE3+–H2O distances are 2.474 A for Sm3+ and 2.450 A for Eu3+. The average RE3+⋅⋅⋅Cl− ion pair distances occur near 4.9 A. A careful examination of the x‐ray diffraction results for ten rare earth chloride solutions indicates that the inner sphere water coordination of the rare earth ions in aqueous solutions decreases from nine to eight due to the decreasing rare earth ionic radii. The ions La3+ through Nd3+ are nine coordinated, those between Nd3+ and Tb3+ are transitional between nine and eight, and those from Tb3+ to Lu3+ are eight coordinated.

The coordination (hydration) of rare earth ions in aqueous chloride solutions from x‐ray diffraction. II. LaCl3, PrCl3, and NdCl3a)

The inner sphere water coordination of the rare earth ions La3+, Pr3+, and Nd3+ in concentrated (3.4 to 3.8 m) aqueous chloride solutions have been determined from x‐ray diffraction measurements. In each solution the rare earth ion exists as the [RE(H2O)9]3+ aquo complex as determined from the quantitative resolution of the radial distribution functions. The average RE3+–H2O distances are 2.580, 2.539, and 2.513 A for LaCl3, PrCl3, and NdCl3, respectively. The average RE3+⋅⋅⋅Cl− ion pair distances are near 5.0 A. These results, together with the octaaquo complex, [RE(H2O)8]3+, found previously for the heavy rare earth ions, Tb3+ through Lu3+, establish that the inner sphere water coordination of the rare earth ions in aqueous solutions decreases from nine to eight between Nd3+ and Tb3+.

High temperature allotropy and thermal expansion of the rare-earth metals

Abstract By means of high temperature X-ray techniques the crystal structure of lanthanum, cerium, praseodymium, neodymium, ytterbium, and possibly gadolinium was found to be body-centered cubic at temperatures near their respective melting points. For ytterbium a hexagonal close-packed structure was also observed, which was shown to be stabilized by atmospheric impurities. Evidence for possible high temperature crystalline transformations in gadolinium, terbium, dysprosium, holmium, and lutetium was obtained by means of electrical resistance measurements; erbium gave no such evidence. X-ray data were used to derive empirical equations which describe thermal expansion coefficients of scandium, yttrium and the rare-earth metals. Europium exhibits a rapidly decreasing coefficient of expansion with increasing temperature, which may be a consequence of a gradual promotion of one of the 4f electrons into the conduction band. The hexagonal rare-earth metals were found to have nearly the same axial ratio at their respective transformation temperatures.

High‐Temperature Heat Contents and Related Thermodynamic Functions of Seven Trifluorides of the Rare Earths: Y, La, Pr, Nd, Gd, Ho, and Lu

The high‐temperature heat contents of high‐purity YF3, LaF3, PrF3, NdF3, GdF3, HoF3, and LuF3 were measured from 100–1600°C. The heat capacity, heats of transition, heats of fusion, and related thermodynamic functions were calculated. The smoothed values of H°T − H°298, Cp, S°T − S°298, and − (F°T − H°298) / T are tabulated at 100° intervals. A comparison of the values for the transition temperature, melting points, and lattice parameters of the higher‐purity fluorides of this work with those of less pure fluorides indicated that a reduction in oxygen content does not affect these properties.

High temperature enthalpies and related thermodynamic functions of the trifluorides of Sc, Ce, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb

The high temperature enthalpies of high purity ScF3, CeF3, SmF3, GdF3 (redetermined), TbF3, DyF3, ErF3, TmF3, and YbF3 were measured from 100 to 1600°C and EuF3 from 100 to 975°C. The thermal data for the other fluorides in the rare earth series were reported earlier from this laboratory. The heat capacity, enthalpies of transition and fusion, and related thermodynamic functions were calculated. The smoothed values of H°T−H°298.15, Cp, S°T−S°298.15, and −(F°T−H°298.15)/T are tabulated at 100° intervals. The melting points, transition temperatures, and lattice parameters of the high purity fluorides prepared in this study were determined.

The atomic heats of the rare-earth elements

The atomic heats of lanthanum, cerium, praseodymium and neodymium have been measured from 2 to 180° K. Lanthanum shows an anomaly corresponding to superconductivity at 4⋅37° K, and the atomic heat (CD) rises to 6⋅2 cal./g. atom at 180° K. The free electronic specific heat deduced from the low-temperature results appears to explain this high value satisfactorily. Cerium, praseodymium and neodymium all behave anomalously. A specimen of cerium of face-centred cubic structure shows an anomaly between 90 and 180° K which exhibits large hysteresis effects. Taking into account the results of other research workers which have been published since this work was begun, this anomaly appears to correspond to the transition of the 4f electron to a 5d state. A second specimen of cerium in which both face-centred cubic and hexagonal close-packed structures were present did not show this anomaly. Both specimens, however, showed large anomalous humps in the low-temperature region at approximately 12° K. Praseodymium shows a very large distributed anomaly which produced a maximum in the atomic heat curve at 65° K. Neodymium shows two anomalous peaks, one at 7⋅5° K and one at 19° K. These anomalies in praseodymium and neodymium, together with the low-temperature anomaly in cerium, can be explained qualitatively by the view that the electronic states attributable to the 4f.electrons are split by the electric fields existing within the metallic crystals. This effect is more complicated than with the magnetically dilute hydrated rare-earth salts, as magnetic interaction is probably very important.

The effect of impurities, particularly hydrogen, on the lattice parameters of the “ABAB” rare earth metals

Abstract The common methods presently used to prepare samples of the heavy rare-earth metals for lattice parameter determinations were shown to give high results due to contamination by interstitial impurities, especially hydrogen. Two methods to produce fine-grained homogeneous samples in the form of wires were established. Both methods have the advantage of not requiring further heat treatment after preparation of the surface to be X-rayed. The lattice parameters of Gd, Tb, Dy, Ho, Er, Tm, Lu, Y and Sc were determined on well-characterized samples. The density, mole atomic volume, atomic radius for CN12, and c a ratios were calculated based on the lattice parameters determined. The effect of hydrogen on the lattice parameters of these metals was determined.

Heat Capacity of Dysprosium from 15 to 300°K

The heat capacity of dysprosium has been measured over the range 15 to 300°K, and the thermodynamic functions have been calculated. Dysprosium had previously been found to exhibit two magnetic transitions and corresponding to these we have observed two maxima in the heat capacity, one at 174°K and a second at 83.5°K. Only the lower peak shows a dependence on the thermal history of the sample and this dependence was investigated. A correlation of the various contributions to the entropy at room temperature indicates that the magnetic contribution is R ln (2J+1). The value of S0298.16 is 17.87 cal (°K)—1 (g atom)—1.

Heat Capacity of Erbium from 15 to 320°K

The heat capacity of erbium has been measured over the range 15 to 320°K and the thermodynamic functions have been calculated. Three maxima have been observed which occur at 19.9°K, 53.5°K, and 84°K. The two at the lower temperatures show a dependence on the thermal history of the sample, and this dependence was investigated. A correlation of the various contributions to the entropy at room temperature has been made and extended to the other rare earth metals.