Abstract: Thermodynamic and structural properties including electrochemical behaviour of LaNi5 and its β hydride are reviewed. The different structural models of the β hydride are discussed. The variations in the hydriding properties as a result of partial substitution of the constituents are presented. Qualitative and quantitative models that relate hydriding characteristics (stability, hydrogen content) to other physical properties (formation enthalpy, unit cell volume, interstitial hole size, electronic structure) of these intermetallics are briefly reviewed. The contribution of the authors concerning the correlation between the stability and the heat of formation of the intermetallic compounds is presented. The crystal structures of some substituted LaNi5 compounds and related hydrides demonstrate the correlation between the absorption capacity and the number of sites occupied by hydrogen atoms.

Abstract: The dielectric constants and dielectric loss tangents of tetravalent titanium-substituted Ni-Zn ferrites Zn 0.25 Ni 0.75 + t Ti t Fe 2−2 t O 4 with various titanium concentrations were measured at room temperature in the frequency range 100 Hz – 500 kHz. The variation of these parameters with composition and frequency is explained qualitatively. Peaks in the dielectric loss tangent versus frequency curves are observed in two of the ferrites. The possible mechanisms are discussed.

Abstract: The effects of annealing on the hysteresis of pressure-composition isotherms for the LaNi 5 H 2 system were examined. It was found that the higher was the annealing temperature before absorption, the higher was the pressure of the subsequent absorption isotherm and eventually the larger was the hysteresis. The dehydrided samples, which were annealed at various temperatures, were subjected to X-ray powder diffraction line profile analysis using the Warren-Averbach method. It was concluded from the results obtained for the crystallite domain size and the lattice strain that the predominant factor affecting the hysteresis is the microstrain in the direction perpendicular to the hexagonal c axis.

Abstract: Fine particles of hydrogen storage alloys such as LaNi5 and MmNi4.5-Mn0.5 (Mm  misch metal) were encapsulated in a thin layer of copper 1–2 μm thick by means of a special chemical plating method. This treatment prevented further disintegration of the metal and improved the thermal conductivity. The alloy-copper microcapsules, which had dimensions of less than 30 μm, were able to absorb hydrogen easily without special activation and exhibited no decrease in hydrogen storage capacity. Pellets obtained by compressing the microencapsulated powder under a pressure of 5–10 tf cm−2 did not show any visible cracks after 1000 hydrogen sorption cycles.

Abstract: The catalytic hydrogenation of acetylene was studied using X-ray diffraction and gas chromatography. The results obtained show that carbon atoms penetrate into the palladium catalyst during the reaction. This process results in the formation of a highly supersaturated solid solution of carbon in the metal, which for kinetic reasons is stable only at moderate temperatures. The crystallographic structure of the solid solution is analogous to that of palladium, with the lattice constant 2.6% higher. The carbon concentration of 11.5 at.% thus obtained is two orders of magnitude higher than that in the saturated Pd-C solution.

Abstract: L'etude par effet Mossbauer des composes Nd 2 Co 14 B dopes avec du fer montre que les atomes de fer ont une forte preference pour occuper le site 8j 2 . Interpretation des resultats en termes de force relative des liaisons et d'effets dimensionnels

Abstract: Resume Cinquante un nouveaux germaniures ternaires ont ete caracterises par analyse radiocristallographique de poudres: 19 isotypes de U 4 Re 7 Si 6 : Lu 4 Ru 7 Ge 6 , R 4 Os 7 Ge 6 (R ≡ Er, …, Lu), R 4 Rh 7 Ge 6 (R ≡ Dy, …, Lu) et R 4 Ir 7 Ge 6 (R ≡ Y, Tb, …, Lu); 28 isotypes de ThCr 2 Si 2 : RRu 2 Ge 2 et RRh 2 Ge 2 (R ≡ Y, La, …, Yb), EuIr 2 Ge 2 ; 4 isotypes de CaBe 2 Ge 2 : RIr 2 Ge 2 (R ≡ La, …, Nd). Trois autres restent a preciser: SmIr 2 Ge 2 et TbIr 2 Ge 2 qui semblent isotypes de CaBe 2 Ge 2 mais avec des parametres singuliers; GdIr 2 Ge 2 dont la maille orthorhombique pourrait etre une variante deformee de celles de type CaBe 2 Ge 2 . Les evolutions structurales observees sont discutees. Parmi les isotypes de ThCr 2 Si 2 ou CaBe 2 Ge 2 a l'yttrium et au lanthane, seul LaIr 2 Ge 2 est supraconducteur au-dessus de 1,4 K ( T C = 1,5 K ).

Abstract: While searching for new Ce- and U-based “heavy fermion” systems, we have investigated the following intermetallic compounds: CeCu 2 Ge 2 , CeCu 2 Sn 2 , CeAg 2 Ge 2 , CeZn 2 Al 2 (tetragonal ThCr 2 Si 2 -structure and modifications thereof); CeRu 3 Si 2 , URu 3 Si 2 (hexagonal LaRu 3 Si 2 -structure); Ce 2 Cu 7 Al 10 , U 2 Cu 7 Al 10 (trigonal Th 2 Mn 17 -structure); CeCu 4 Al 8 , CeAg 4 Al 8 , UCu 4 Al 8 (tetragonal CeMn 4 Al 8 -structure); LaCu 13− x Al x with x = 3, 5.5, and 6.5, as well as CeCu 6.5 Al 6.5 (cubic NaZn 13 -structure). Resistive and inductive measurements were undertaken between T = 30 mK and room temperature, and two new superconductors were found: LaCu 6.5 Al 6.5 ( T c = 0.65 K) and CeRu 3 Si 2 ( T c = 1.2 K). The specific heat and thermopower of two of these systems have also been measured. CeCu 4 Al 8 shows interesting features that are presumably related to fine structure in the “heavy-fermion” density of states near the Fermi level. CeCu 6.5 A1 6.5 shows a magnetic transition at T = 0.5 K which resembles a “spin-glass freezing” rather than a formation of long-range magnetic order.

Abstract: In the ternary ScAlN system a perovskite-type phase Sc3AlN1 − x (a = 0.4396–0.4435 nm) occurs at 1273 K. This phase is in equilibrium with ScN, Sc(solid solution), Sc2Al and ScAl. AlN does not coexist with scandium but does so with ScN, ScAl2 and ScAl3. The binary phase ScAl was found to be orthorhombic with a = 0.502 99 nm, b = 0.989 45 nm and c = 0.312 63 nm. In the Y-Al-N system no ternary phase was found. AlN reacts with up to 40 at.% Y to yield YN and YAl2. Isothermal sections at 1273 K are presented for both ternary systems.

Abstract: Investigations by neutron diffraction and magnetic measurements are reported on the ternary suicides RRh2Si2 (R  Ce, Nd, Tb) and RRu2Si2 (R  Nd, Tb) with the tetragonal structure of the ThCr2Si2 type. CeRh2Si2 orders antiferromagnetically below 36 K with a wave vector k = [ 1 2 1 2 0] and magnetic moments parallel to the c-axis (m0) = 1.50 μ/Ce). The magnetic structure of TbRh2Si2 is antiferromagnetic (k = [001]) below TN = 94 K, the magnetic moments (8.5 μB/Tb at T = 15 K) are also parallel to the c-axis. NdRh2Si2 has the same magnetic structure below TN = 57 K, with m0 = 2.80 μB/Nd parallel to the c-axis. NdRu2Si2 exhibits a more complicated magnetic structure: below TN = 24 K it develops a sine-wave modulation (k = [0.130.130]) of the magnetic moments always parallel to the c-axis, with an amplitude Ak = 3.23 μB/Nd; a squaring of the magnetic structure occurs at about 15 K (m0 = 2.84 μB), and at T

Abstract: The new ternary uranium and cerium compounds UCu4Al8, U2Cu7Al10, URu2Si2, CeCu6.5Al6.5, CeCu2Sn1.9 and CeZn2Al2 have been prepared and structurally characterized.

Abstract: Some aspects of lanthanide-organic ligand interaction in aqueous solutions are reviewed. Thermodynamic parameters ( ΔG , ΔH and ΔS ) of complexation are interpreted in terms of hydration, inner versus outer sphere character, stability versus chelate ring size and ligand charge polarization.

Abstract: The lanthanide elements are widely used as optical structural probes in solid state chemistry. Group theory and line positions are used to derive the symmetry and the number of crystallographic sites. For some compounds additional lines or illogical splittings make interpretation difficult. The Stark level widths depend on the phonon density of states in the material: if it is a continuous function the classical theory applies well, but if the phonon density of states is resolved into sharp peaks, zero-phonon line splittings may occur from resonance effects, with sharp phonons corresponding to the energy difference between Stark levels. Examples are shown for lanthanide organic compounds, and for some inorganic phases as well. Vibronic satellites occur prominently in some phases, especially if tetrahedral anions (phosphate etc…) are present. From the vibronics associated with simple electronic transitions it is possible to derive an effective density of phonon states. The puzzling case of Eu3+ in GdNbO4, where the fine structure of the emission spectrum depends on the optical excitation wavelength, is presented.

Abstract: A new investigation of the structure of the β-LaNi5Dx deuteride has been performed using neutron diffraction over a wide range of deuterium concentration (5.0 ⩽x ⩽ 6.7). By increasing the deuterium content, we show that the deuteride undergoes a structural phase transformation due to a progressive ordering of D atoms. This results in a reduction of symmetry and in a superstructure which corresponds to a doubling of the LaNi5 unit cell along the c axis. We propose a new model for the structure of β-LaNi5Dx (5.0 ⩽ × ⩽ 7.0) which is described in the P63mc space group. In this model the ordering of deuterium is characterized by a parameter a which varies linearly from zero to one as x increases from 5 to 7 D per LaNi5. In the fully ordered LaNi5D7 phase deuterium would occupy four types of interstitial sites.

Abstract: The six families of binary rare-earth (RE) borides are reviewed: REB 2 , REB 4 , RE 2 B 5 , REB 6 , REB 12 and REB ~66 . The existence of these compounds and their crystal structures are discussed knowing that metal atoms contribute both geometrically and electronically to the stabilization of the electron-deficient boron framework. Emphasis is focused on the ability of metal or non-metal impurities either to stabilize a particular structure or to modify drastically the electrical and magnetic properties of the borides. Hexaborides are chosen to illustrate this point. The physical properties of some significant compounds are highlighted: ErB 4 and HoB 4 (magnetic phase transition), YbB 4 , YbB 12 and SmB 6 (intermediate-valence state), CeB 6 (dense Kondo-like behaviour), EuB 6 (ferromagnetic semiconductor), LaB 6 (thermoelectronic emitter) and YB 6 (superconductor).

Abstract: The rare earths community is small and restricted and needs better communication between production, end users, and research. This paper gives a general overview of RE reserves, production capacity, and also a breakdown of the consumption by end users. Among the permanent problems of RE producers, three are of greatest importance: 1. (i) Balancing the market demand with the natural occurrence of the RE elements in most common ores such as monazite and bastnasite. This is essential in ensuring the lowest market price for any RE element. 2. (ii) The extreme speed of development of some new applications. 3. (iii) The difference in growth rates of various applications.

Abstract: An isothermal section of the Ni-Cr-Al system at 1423 K has been investigated using Knudsen cell mass spectrometry to determine the activities of nickel, chromium and aluminium. These data provide independent measurements, i.e. without the need for integration, of all of the components, both in the binary and ternary systems. The data on the binaries are mutually consistent, as can be seen by the comparisons given between the experimental results and values obtained by integration.

Abstract: As a result of the systematic evaluation of about forty published molecular structures of organolanthanoid(III) complexes, the so-called “solid-angle-sum (SAS) rule” suggests that optimal coordinative saturation is verified for the comparatively small SAS value of 0.73. Here, 4π·SAS is the sum of the individual solid angles of all ligands surrounding one central metal ion (Ln3+). On the basis of empirical standard values of the “solid angle factors”, SAF = SA 4π , of various frequently occurring ligands, the SAS-rule allows reasonable predictions to be made of the relative stabilities of distinct members of numerous complex families, particularly as a function of the ionic radius of the respective central metal ion (including also La3+, Y3+ and Sc3+).

Abstract: Two series of metastable, cubic face-centered non-stoichiometric anti-glass tellurates of Y, La, and lanthanides have been found: Te-richer phases, containing tetravalent Te only, with compositions between Ln 2 Te 6 O 15 and Ln 4 Te 7 O 20 and lattice constants of 570−549 pm, and Ln-richer phases containing minor amounts of hexavalent Te, with Ln:Te ratios between 3:2 and 11:10, and lattice constants between 574 and 539 pm.

Abstract: The three-dimensional stability diagram developed for binary systems to predict compound formation is applied to ternary systems The separation into systems forming compounds and systems not forming compounds is based on the experimental data of 7200 ternary systems This method of separation is accurate to 94%

Abstract: Resume Quarante-sept nouveaux germaniures ternaires ont ete caracterises par analyse radiocristallographique de poudres: 34 isotypes de Yb 3 Rh 4 Sn 13 : TR 3 Co 4 Ge 13 (TR ≡ Y, Sm, Gd, …, Lu), TR 3 Rh 4 Ge 13 (TR ≡ Y, Nd, Sm, Gd, …, Lu) et TR 3 Ir 4 Ge 13 (TR ≡ Y, Ce, …, Sm, Gd, …, Lu), et 13 isotypes de BaNiSn 3 : TRCoGe 3 (TR ≡ La, …, Nd, Eu), TRRhGe 3 (TR ≡ La, …, Pr, Eu), TRIrGe 3 (TR ≡ La, Eu), LaRuGe 3 et LaOsGe 3 . Les evolutions structurales observees sont discutees.

Abstract: Ternary alloys of the rare earths (R) with tin and nickel or palladium in the stoichiometric ratio 1:1:1 were studied. It was confirmed that these alloys have structures belonging to the CeCu2 family (oI12 (CeCu2) or oP12 (TiNiSi) types). The behaviour of the average atomic volumes of these phases is compared with the behaviour of other series of similar compounds, and the general properties of several RTSn alloys are briefly summarized.

Abstract: The Miedema-Niessen model for the volume effects which occur when two transition metals are alloyed is applied to the fast diffusion of metallic impurities in metals. The use of the model is also extended to other metallic systems. A correlation is found between fast diffusivities and the volumes corrected using this model. A similar correlation is found for the activation volumes for the diffusion of impurities in lead. The difference in the diffusion behaviour of gold and silver, which have equal uncorrected volumes, can be explained. It can be understood why gold is a fast diffuser in lead, praseodymium, thallium, indium and zinc, but not in γ-U although other impurities are fast diffusers in this metal. Predictions are made for other fast-diffusing systems.

Abstract: The phase equilibria in the transition-metal-rich area of the ternary SmCoFe system have been investigated to determine the Fe solubility in those intermetallic phases occurring in the binary SmCo system. Complete miscibility of Co and Fe is found for the three phases Sm2(Co, Fe)17, Sm(Co, Fe)3, and Sm(Co,Fe)2; whereas only limited Fe solubility exists in SmCo5, Sm2Co7, Sm9Co4, and Sm3Co. No ternary phase forms. Computer calculations of the binary systems SmCo, SmFe and CoFe were carried out using all the thermodynamic and phase diagram data from the literature. On the basis of this description the ternary SmCoFe system was extrapolated and compared with our own experimental results.

Abstract: The radiative transitions of trivalent rare earth ions in transparent media can be calculated using the three intensity parameters Ω 2 , Ω 4 and Ω 6 and the three matrix elements U2, U4 and U6 connecting any pair of electronic levels of the 4fN configuration. The multiphonon relaxation rates between any pair of electronic levels are determined by two phenomenological parameters α and B which are matrix dependent only. The paper presents a full set of Ω parameters, allowing calculation of radiative transition probabilities in oxide and fluoride crystalline media, and comparison in the amorphous media of oxide, chalcogenide, and fluoride glasses. The phenomenological parameters α and B are tabulated for the same systems. Connections are deduced between the values of the phenomenological parameters, the electronic structure of the ion involved and the chemical nature of the host matrix. An example of cross-relaxation of Ho3+, Nd3+ and Tb3+ represents an additional channel for nonradiative relaxation. The above presented values enable a priori calculations of efficiencies of solar concentrators and cross-sections for laser emission.

Abstract: Several alloys close in composition to Nd 2 Fe 14 B and Nd 2 Co 14 B were investigated by standard metallography. It was found that the tetragonal Nd 2 Fe 14 B-type structure applies also to Nd 2 Co 14 B. This structure does not tolerate significant deviations from stoichiometric composition. Annealed off-stoichiometric alloys are composed of impurity phases, the presence of which can have an unfavourable effect on the magnetic properties. The Curie temperature of Nd 2 (Fe 1− x Co x ) 14 B was studied as a function of composition in the range 0 ⩽ x ⩽ 0.6. The compound Th 2 Fe 14 B also crystallizes in the tetragonal Nd 2 Fe 14 B-type structure. Its Curie temperature is 480 K and the room temperature anisotropy field is of the order of 3 T. From a study of the 57 Fe Mossbauer spectra of Nd 2 Fe 14 B and Th 2 Fe 14 B it was deduced that different crystallographic iron sites give rise to different sizes of the iron moments, the average iron moment in Th 2 Fe 14 B being only slightly lower than that in Nd 2 Fe 14 B.

Abstract: Fe2Ta9S6, Co2Ta9S6, and Ni2Ta9S6 have been prepared by high temperature techniques. The crystal structure has been determined from single crystal X-ray diffraction data for Fe2Ta9S6 (R = 0.042) and Ni2Ta9S6 (R = 0.031). The hexagonal cell contains one formula unit. The tantalum substructure can be viewed as condensed clusters consisting of tetrakaidecahedra sharing faces along the c axis and vertices in the hexagonal plane. The tantalum clusters are additionally bridged by low coordinated sulfur atoms sheathing channels of about 400 pm diameter which run along the c axis. The iron-group metal occupies centers of the tricapped trigonal tantalum prisms. Anomalies in the lattice parameters of Ni2Ta9S6 are discussed.

Abstract: The laser-induced fluorescence line narrowing method, using the optical properties of Eu3+-doped oxide glasses, has been used to investigate the local structure and structural inhomogeneities of glasses. Recent contributions are reviewed which indicate the present state of knowledge and new results obtained for these materials, which show a discrete site distribution instead of the usual site continuum, are reported.