Cerium Valence Change in the Solid Solutions Ce(Rh 1-x Rux)Sn

Zeitschrift anorg allge chemie

Janka

2015

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Section: Resultsmentioning

confidence: 99%

Gradual Cerium Valence Change in the Solid Solution CeRu_1–xPd_xAl (x = 0.1–0.9)

Zeitschrift anorg allge chemie

Janka

2015

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“…The last point has already been discussed several times in literature [44][45][46]. In the case of CeCoAl a fitting with the ICF-model [44] leads to physical unrealistic values, consequently only Curie-Weiss fitting remains.…”

Section: Physical Propertiesmentioning

confidence: 92%

Intermediate-valent CeCoAl – a commensurate modulated structure with short Ce–Co distances

Zeitschrift Für Kristallographie - Crystalline Materials

Hoffmann

Tencé

et al. 2015

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CeCoAl was synthesized by melting of the elements in a sealed niobium tube in an induction furnace. Annealing of the sample gave access to a single phase sample. Its structure was refined on the basis of single-crystal X-ray diffractometer data at different temperatures. Above 271 K CeCoAl crystallizes in its own structure type in the space group C2/m [a = 1107.4(2), b = 440.6(1) and c = 479.6(1) pm, β = 104.6(1)°]. Data obtained at 300 K lead to 511 F 2 values with 20 variables and a residual of [I ≥ 3σ(I)] wR = 0.0539. Below 271 K satellites give rise to the superspace group C2/m(α0γ)00; α = 2/3, γ = 2/5 with a temperature independent q-vector. For the 90 K data (also for 180 and 220 K) the commensurate modulated structure could be refined with 4817 F 2 values, 129 variables and residuals of wR = 0.0347 (main), wR = 0.1927 (satellites 1st order), wR = 0.1541 (satellites 2nd order) and wR = 0.1768 (satellites 3rd order) [a = 1107.5(1), b = 440.3(1) and c = 479.0(1) pm, β = 104.7(1)°]. For the three temperatures only minor variations of the modulation amplitudes are observed. The relation of the low temperature (3+1)D 3a × 5c approximant and the room temperature 3D structure is discussed on the basis of a group-subgroup relation. By investigation of the heat capacity, the phase transition could be identified as a second order one with a transition temperature of 271 K. Magnetic measurements clearly prove the intermediate cerium valence which is in line with the short Ce-Co distances.

“…As already proven for the solid solution Ce(Rh 1−x Ru x )Sn, X-ray absorption spectroscopy (XAS) at the CeL III edge is to be considered a powerful tool for studying the valence state in cerium compounds [14]. XANES gives a relevant representation of the electronic configuration yielding the 4 f occupation number.…”

Section: Xanes -X-ray Absorption Near Edge Structurementioning

confidence: 99%

“…Our first experiments concentrated on the solid solution Ce(Ru 1−x Rh x )Sn [14]. Upon small degrees of Ru/Rh substitution, the structure readily switches to the hexagonal ZrNiAl type of CeRhSn.…”

Section: Introductionmentioning

confidence: 99%

The Solid Solutions (Ce_1-xLa_x)RuSn

Zeitschrift Für Naturforschung B

Chevalier

Abdala

et al. 2013

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X-Ray-pure samples of the solid solutions (Ce 1−x La x )RuSn were obtained up to x = 0.5. Powder diffraction data show the CeRuSn-type superstructure up to x ≈ 0.3 and the CeCoAl-type subcell for higher lanthanum contents. The structure of a single crystal with x = 0.5 was refined on the basis of single-crystal X-ray diffractometer data: CeCoAl type, C2/m, a = 1160.8(2), b = 477.6(1), c = 511.6(1) pm, β = 102.97(2) • , wR = 0.0510, 444 F 2 values, 20 variables. Magnetic investigations were performed for all samples up to a lanthanum content of x = 0.4. No cooperative phenomena could be observed, and all samples show Curie-Weiss behavior above a certain temperature. The cerium valence is about 3.32(2) for all samples of the solid solution. Hence, La 3+ has to replace Ce 3+ as well as Ce 4+ in a particular quantity. The electrical resistivity measurements confirm the suppression of the magnetic ordering and the structural transition upon replacement of cerium by lanthanum. 119 Sn Mössbauer spectra of samples with x = 0.2 and 0.5 are indicative of single tin sites with isomer shifts of δ = 1.86(1) mm s −1 for x = 0.2 and δ = 1.88(1) mm s −1 for x = 0.5. Both signals are subject to significant quadrupole splitting, a consequence of the low site symmetry. Results of XANES measurements are perfectly in line with the cerium valences determined by susceptibility measurements and yield a constant value of 3.16(1) for all investigated compounds.