Solid Solution Ce Research Articles

Relation between lattice parameters and valence state of Cu ions of MxNd 2− xCuO 4− y ( M = Na and Ce) solid solution

The lattice parameters, the oxygen content, and the electrical and magnetic properties of M x Nd 2− x CuO 4− y ( M = Na and Ce) with the Nd 2CuO 4 structure have been determined by means of X-ray powder diffraction, thermogravimetry, electrical resistivity, and magnetic susceptibility measurements. The oxidation states of Cu were estimated from the measured y values and the nominal composition x, on the basis of charge neutrality. The composition dependence of the lattice parameters is discussed by taking the oxygen content, the ionic radii, and ( Cu + Cu ) into consideration. The formation of holes and electrons on the CuO bond within the basal plane is discussed in terms of the CuO bond length in the structure of the host materials.

Optical properties of Ce 1− xPr xO 2 powders and their applications to the coloring of ceramics

The development of red pigments with high temperature stability is of great importance for the ceramic industry. Stabilization of praseodymium (IV) in the refractory oxide CeO 2 leads to cerium-rich solid solutions Ce 1− x Pr x O 2 in the red coloration range. Crystallographic and optical properties have been investigated. The detected color is consistent with Jørgensen's model. Thermal stability at high temperature has been studied for various glazes.

Oxidation and phase behaviour studies of the U-Ce-0 system

Oxidation of mixed urania-ceria solid solutions results in variable oxidation products, the stoichiometry and phase behaviour of which depend on the cerium content and temperature. In the present work, air oxidation and phase behaviour studies were carried out covering the compositional range 2.5 to 90 a% cerium and a temperature range of 873–1273 K. Oxygen-to-metal ratios corresponding to the limiting oxidation on the hyperstoichiometric side were measured and the phases identified. Cerium solubility in U 3O 8 as well as the cerium content required to stabilise the single phase fee M'O 2+x (M' = U + Ce) solid solution against further oxidation were investigated at temperatures of 873, 1123 and 1273 K. Variation of the mean uranium valency in the oxidised solid solutions as a function of the cerium content and temperature was also elucidated.

Hall effect in CeAl 3

We have studied temperature dependences of the Hall coefficient R H(T) and resistivity ϱ(T) in substitutional solid solutions Ce xLa 1−xAl 3 (0 ≤ x ≤ 1) which realize the transition from Kondo impurity regime (X⪡1) to Kondo lattice ( X = 1). Lowering temperature results in the anomalous increase of R H(T). The ratio r = R H (3 K)/ R H (100 K) has been found to increase with cerium content up to the r ≅ 15 in the marginal compound CeAl 3. The specific features of R H(T) behaviour in Ce xLa 1−xAl 3 alloys seem to be related to the existence at low temperatures of heavy fermions due to the formation of the narrow Abrikosov-Suhl resonance at the Fermi level.

The AgCe phase diagram II: Ag3CeCe partial phase diagram and general discussion

Abstract The AgCe system was re-examined to clarify discrepancies reported in the literature. The phases Ag 3 Ce (hexagonal, Ag 3 Pu type), Ag 2 Ce (orthorhombic, CeCu 2 type) and AgCe (b.c.c.) are found to be present in the Ag 3 CeCe partial phase diagram. Ag 3 Ce and AgCe melt congruently at 1030 °C and 855 °C respectively. Ag 2 Ce is formed peritectically at 855 °C by the reaction between Ag 3 Ce and the liquid. The eutectic reactions liquid → Ag 3 Ce + AgCe liquid → AgCe + Ce solid solution occur at 780 °C and 505 °C respectively. The high temperature modification δ-Ce dissolves up to 2 at.% Ag and decomposes metatectically at 710 °C: δ-Ce → liquid + γ-Ce The phase diagram is based on the results of thermal analysis and microstructure examination of cast and slowly cooled specimens. In addition, the complete AgCe system is presented and the lattice structures of the intermetallic compounds are summarized.

The appearance of the many-body resonance at the Fermi level in Kondo-lattices

Studing transport and magnetic properties of solid solutions Ce xLa 1−xCu 2Si 2 (0≤ x ≤ 1) and using for CeCu 2Si 2 pressure p as an external parameter, we have observed the continious transition from Kondo-impurity regime ( x « 1 ) to Kondo lattice ( x ⋍ 1, p = 0, ν Ce ≈ 3+ ) and then through the intermediate valence state (x = 1, 0 < p < po ≠ 0, 3+< νCe < 4+) to metal with ν Ce⋍ 4+ . We have found that all the anomal ous properties of Kondo-lattices (CeCu 2Si 2, CeAl 3, CeAl 2) are caused by the appearance at the Fermi level of the many-body resonance of Abrikosov-Suhl type.

Intermediate valence effects in the magnetic behaviour of Ce (Rh xPt 1−x) 2 laves phase compounds

The complete series of solid solutions Ce (Rh xPt 1−x) 2 (0 ≤ × ≤ 1) present a single cubic phase C15. The magnetic susceptibility and lattice parameters were measured, showing a big change in the temperature dependence of the susceptibility, which is explained as a change in the valence of the Ce ions, from 3+ (CePt 2) to 3.5+ (CeRh 2). This is supported by the lattice parameter study, which shows a non-linear relationship of the lattice parameter with the concentration x. We compare our results with previous works, and we also found a T 2 dependence for the susceptibility in the low temperature region for the compounds presenting intermediate valence. This can be explained in the light of the Fermi liquid theory.

Magnetic and electrical properties of rare earth dicarbides and their solid solutions

The magnetic and electrical properties of the CaC 2-type rare earth dicarbides are reported. The Néel temperatures and magnetic resistivities of heavy rare earth dicarbides are discussed in the light of the Ruderman-Kittel-Kasuya-Yosida theory. The magnetic resistivities of the solid solutions Ce x La 1− x C 2 are discussed on the basis of the Γ 7 components of Ce 3+. The influence of the change in the crystal structure (b.c.t. → f.c.c.) on the superconducting transition temperatures is examined for the solid solutions La x Y 1− x C 2.

Metastable f.c.c. PuCe solid solutions

With the exception of one composition (75 at.% Ce), single-phase, metastable Pu  Ce alloys have been produced over the complete composition range by splat-cooling. Three f.c.c. CuA1 type phases can be distinguished: γCe(Pu) solid solutions, a metastable phase designated α 1 Ce(Pu) between ∼ 20 and 75 at.% Ce, and δPu(Ce) solid solutions with lattice parameters which extrapolate to that of αCe. As inferred from lattice parameter data, a sudden electronic transition from trivalent γCe to that of a higher valent α 1 Ce occurs at ∼ 75 at.% Ce. With increasing Pu content, a further, gradual Ce valence increase to the valence of αCe was observed.