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• 7440-45-1 cerium 
• 7440-21-3 silicon 

Relevant academic research and scientific papers

Ce4(Pi-xSix)3-z: A first example for the stabilization of the anti-Th3P4 type structure by substitution in the non-metal substructure

A first rare-earth phosphide suicide Ce4(P1-xSi x)3-z and its analogues with La, Pr, and Nd were synthesized and characterized. The compounds crystallize in the anti-Th 3P4 structure type. The cerium compound shows a mixed occupation of the 12a site with Si and P and possesses a wide homogeneity range with respect to x and z variation. The electronic configuration of Ce, deduced from magnetic susceptibility and X-ray absorption spectroscopy data, remains 4f1 (Ce3-) independently from x and z. The cerium valence and the phase stability region are discussed employing electronic band-structure calculation and chemical bonding analysis with electron localization function. Atomic interactions are shown to remain nearly unchanged, while the change of the excess electron concentration with P/Si substitution is considered to play the main role for the stabilization of the structural motif.

High-resolution angle-resolved photoemission study of CeP: Narrow-band formation of 4f electrons

High-resolution angle-resolved photoemission spectroscopy at low temperature has been performed on the low-carrier Kondo material CeP. It was found that the p-f bonding state with a dominant 4f character exhibits a finite-energy dispersion of about 40 meV along the ΓX direction in the Brillouin zone. This implies that 4f electrons in CeP form a narrow band owing to the strong anisotropic p-f and d-f mixing.

Third time's the charm: Intricate non-centrosymmetric polymorphism in Ln SiP3(Ln = la and Ce) induced by distortions of phosphorus square layers

Complex polymorphic relationships in the LnSiP3 (Ln = La and Ce) family of compounds are reported. An innovative synthetic method was developed to overcome differences in the reactivities of the rare-earth metal and refractory silicon with phosphorus. Reactions of atomically mixed Ln + Si with P allowed for selective control over the reaction outcomes resulting in targeted isolation of three new polymorphs of LaSiP3 and two polymorphs of CeSiP3. In situ X-ray diffraction studies revealed that the developed method bypasses formation of the thermodynamic dead-end, the binary SiP. Careful re-determination of the crystal structure ruled out the previously reported ordered centrosymmetric structure of CeSiP3 and showed that the main LnSiP3 polymorphs crystallize in the non-centrosymmetric Pna21 and Aea2 space groups featuring distinct distortions of the regular P square net to yield either cis-trans 1D phosphorus chains (Pna21) or disordered-2D phosphorus layers (Aea2). The disordered 2D nature of the P layers in the Aea2 LaSiP3 polymorph was confirmed by Raman spectroscopy. A unique centrosymmetric P21/c polymorph was observed for LaSiP3 and has a completely different crystal structure lacking P layers. Consecutive polymorphic transformations at increasing temperatures for LaSiP3(Pna21 → P21/c → Aea2) were derived from optimized synthetic profiles and confirmed by a combination of phonon computations and experimental in situ and ex situ annealings. Crystal structures of the LaSiP3 polymorphs were verified via advanced solid state NMR analysis using 31P MAS and 31P{139La} double resonance techniques. A combination of phonon and electronic structure calculations, NMR T1 relaxation times, UV/Vis/NIR spectroscopy, and resistivity measurements revealed that all the reported polymorphs are semiconductors with resistivities and thermal conductivities strongly dependent on the degree of distortion of P square layers in the crystal structure. Reported here, non-centrosymmetric LnSiP3 polymorphs with tunable resistivity and thermal conductivity provide a platform for the development of novel functional materials with a wide range of applications.

Chemical pressure effect in CeFeAs1-xPxO 0.95F0.05

We investigate the chemical pressure effect due to P doping in the CeFeAs1-xPxO0.95F0.05 (0≤x≤0.4) system. The compound CeFeAsO0.95F0.05 without P doping is on the boundary between antiferromagnet (AFM) and superconductor. The AFM order of Ce3 local moments causes a significant reentrance behavior in both resistivity and magnetic susceptibility. Upon P doping, Tc increases and reaches a maximum of 21.3 K at x=0.15, and then it is suppressed to lower temperatures. Meanwhile, the AFM order of Ce3 ions remains nearly the same in the whole doping range (0≤x≤0.4). Our experimental results suggest a competition between superconductivity and Kondo effect in the Ce 1111 system.

RE4[P1-x(C2)x]3 (RE = La-Nd): The mixed anionic substructure formed by phosphorus and carbon

The rare-earth phosphide carbides RE4[P1-x(C 2)x]3 (RE = La, Ce, Pr, Nd) represent the first example of a mixed anionic substructure formed by phosphorus and carbon, being the first step toward the formation of the mixed inorganic P-C species. The peculiarities of the crystal structure, magnetic properties, XAS data, and quantum chemical calculation results confirm the ionic nature of the interaction beween the rare-earth cations RE and phosphorus anions, while complex interaction of π states of the C2 anions and d (and/or f) states of the RE components is indicated. Thus, despite the extensive chemical analogy between the phosphide carbides and phosphide suicides, the atomic interactions stabilizing the structural motif are slightly different.

Phase transitions of lanthanide monophosphides with NaCl-type structure at high pressures

Lanthanide monophosphides LnP (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Tm and Yb) with a NaCl-type structure have systematically been prepared at high temperatures. Using synchrotron radiation, X-ray diffractions of LnP have been studied up to 61 GPa at room temperature. The NaCl-CsCl transition for CeP is found at around 25 GPa. First-order phase transitions of LnP (Ln = La, Pr and Nd) with the crystallographic change occur at around 24, 26 and 30 GPa, respectively. The structure of the high pressure phases of these phosphides is a body center tetragonal structure (Ln: 0, 0, 0; P: 1/2, 1/2, 1/2; space group P4/mmm), which can be seen as the distorted CsCl-type structure. The Pr-P distance in the high pressure form of PrP is 2.789 A. This almost agrees with the sum of covalent radii of Pr and P. The Pr-P bond has the covalent character at very high pressures. Similar results are also obtained for LaP and NdP. The pressure-induced phase transitions of SmP, GdP, TbP, TmP and YbP occur at around 35, 40, 38, 53 and 51 GPa, respectively. The structure of the high pressure phase is unknown. The phase transitions of LnP with many f-electrons are not due to the mechanism of the ordinary NaCl-CsCl transition. The transition pressures of LnP increase with decreasing the lattice constants in the NaCl-type structure, which decrease with increasing atomic number of the lanthanide atoms.

Phase Equilibria in the {La, Ce}-Fe-P Systems

Isothermal sections of the La-Fe-P and Ce-Fe-P phase diagrams at 1070 K (up to 30 mol% of a rare-earth metal) and at 870 K (30-100 mol %) are constructed by using X-ray diffraction techniques. The compounds LaFe2P2, CeFe2P2, and Ce2Fe12P7 are synthesized by direct reaction of the constituent elements at the temperature of investigation.