Praseodymium Compounds Research Articles

Evidence of Kondo effect in thermal conductivity of PrSn3

Abstract We present measurements of the thermal conductivity of both PrSn3 and LaSn3 compounds. We deduce the “magnetic thermal resistivity” Wmag of PrSn3 and show that WmagT exhibits a Log T behavior characteristic of the Kondo effect. The theoretical analysis of the thermal conductivity measurements offers a new method to study the Kondo effect, especially in the case of a praseodymium compound.

Magnetic behaviour of the tetravalent praseodymium compoundSr2PrO4

We report on investigations of the magnetic properties of the tetravalent praseodymium(Pr4+)compound Sr2PrO4 by dc and ac magnetic susceptibility and heat capacity measurements.The compound shows signatures of long range magnetic order atTN = 3 K in the heat capacity and magnetization data. In addition, the temperature dependence ofthe field cooled and the zero-field cooled susceptibility is hysteretic below 10 K. Heat capacityversus temperature data show that a significant part of the magnetic entropy is released aboveTN.This reveals that short range magnetic correlations among the Pr moments exist well aboveTN.The magnetic entropy obtained from the heat capacity measurements indicates that onlythe crystal field ground state of Pr with effective spin- is significantly populated at low temperatures.

Electronic spectroscopy (Pr3+) and crystal field parameter calculations (Eu3+) for complexes of formula [Ln(2,2′-bipyridine-1,1′-dioxide)4](ClO4)3

This paper is a continuation of our earlier studies on the excited state dynamics of high symmetry [Ln(2,2′-bipyridine-1,1′-dioxide)4](ClO4)3 systems. It was shown that all RE ions form, with the title ligand (bpyO2), complexes of formula [Ln(bpyO2)4](ClO4)3 and are eight-coordinated by oxygen atoms of the bpyO2 molecules. The praseodymium compound crystallizes in the monoclinic system, P21/c, with a=14.57(1), b=13.57(1), c=22.80(10) Å, β=92.00(7)° and Z=2. Electronic absorption spectra of [Pr(2,2′-bipyridine-1,1′-dioxide)4](ClO4)3 in solid state, in acetonitrile and nitromethane solutions were measured in the spectral range from 400 to 2200 nm. The probabilities of f–f transitions and Judd–Ofelt parameters are analysed in the frame of intensity polarizability mechanism and compared to other high symmetry systems. The partial energy level diagram of Pr(III) terms was derived on the basis of absorption spectrum of the complex at 4 K. The crystal field parameters for Eu(III) were calculated from the experimental set of Stark components of high resolution emission spectra recorded at 77 K in the range of 5D0→7FJ (J=0–6) transitions under UV excitation. Satisfactory correlation was found between the experimental and fitted energy levels.

Crystal structure, magnetism and photophysics of the lanthanide maleates RE(C4O4H3)3·8H2O (RE=Nd, Sm)

This article reports the results of an X-ray study, of the magnetic and spectroscopic characteristics of lanthanide maleates. An X-ray single crystal structure determination was performed for Nd(C4O4H3)3·8H2O. The crystal structure is triclinic (P1, Z=2, a=7.285(1) Å, b=10.394(2) Å, c=16.765(3) Å, α=72.13(2)°, β=87.77(2)°, γ=70.86(2)°, Rall=0.0322) and isotypic with the respective praseodymium compound. Nd3+ is nine-fold coordinated by oxygen atoms in the form of a tricapped trigonal prism. Two carboxyl groups of two crystallographically independent hydrogenmaleate ions are attached to Nd3+ in a monodentate manner. The third hydrogenmaleate anion forms hydrogen bonding with unbound and coordinated water molecules. Thus, the crystal structure of the title complexes points to an unusual carboxyl group coordination with lanthanide ions. Absorption spectra of neodymium and samarium single crystals at 293 and 4.2 K were recorded. Analysis of the f–f transition probabilities were performed and Judd–Ofelt parameters were determined. Strong vibronic coupling was found, mainly promoted by modes which correspond to co-ordinated moieties of ligand molecules. A structural transformation is expected based on the relatively high temperature factors in the X-ray data. This was confirmed by the spectroscopic investigation. Magnetic susceptibility results were correlated with X-ray data and results reported previously.

Synthesis and spectroscopic characteristics of a new class of lanthanide compounds of formulae Ln(HX) 3(NO 3) 3 and Ln(HX) 3Cl 3

Two series of the lanthanide (Eu, Pr) compounds of the formulae Ln(HX) 3Cl 3 (1); Ln(HX) 3(NO 3) 3 (2) [where HX=CCl 3CO–NH–PO(NEt 2) 2] with C.N.=6 and 9 were obtained in the form of monocrystals. The spectroscopic properties of these compounds were investigated at 293, 77 and 4.2 K and the results related to their structures. Correlation was made with the spectroscopic data and structure of the Eu and Nd respective chelates. Essential differences were found in coordination mode of ligand molecules in those systems. Intensity analysis of electronic transitions, electron–phonon coupling, as well as splitting and energies of electronic levels were used as tests of metal bonding in the systems under investigation. The electronic f–f transitions of praseodymium (1, 2) compounds show drastic differences in oscillator strength values, pointing thus at substantial differences in symmetry of the metal centre. Judd–Ofelt parameters were calculated with low errors of estimation. The relatively strong vibronic lines appear at displacement frequencies, corresponding to both ligand and Ln–L n localised vibrational modes.

Mean-field phase diagram for cubic-based praseodymium compounds

Calculating the exact mean-field free energy from a Heisenberg-like Hamiltonian we determine the magnetic phase diagram for cubic-based praseodymium compounds with a ${\ensuremath{\Gamma}}_{3}$ doublet ground state and a ${\ensuremath{\Gamma}}_{4}$ triplet first-excited state. We find lines of first- and second-order phase transitions, separated by a tricritical point. We also calculate the temperature dependence of the magnetic-order parameter.

The Series of Rare Earth Zinc Phosphides RZn3P3 (R=Y, La–Nd, Sm, Gd–Er) and the Corresponding Cadmium Compound PrCd3P3

The 12 title compounds were prepared by reaction of the elemental components in a NaCl/KCl flux. Their isotypic crystal structures were determined for the two praseodymium compounds from single-crystal X-ray data in the space group P63/mmc with Z=2 formula units per cell; PrZn3P3: a=404.0(1) pm, c=1997.9(6) pm, R=0.064 for 253 structure factors; PrCd3P3: a=426.5(1) pm, c=2090.6(6) pm, R=0.020 for 309 F values and 14 variables each. Large displacement parameters for one-third of the zinc, cadmium, and phosphorus sites of both structures indicate distortions. Hence, the true symmetry of both compounds may be lower, as is known for the closely related structure of ScAl3C3. The cadmium and phosphorus atoms of PrCd3P3 form triple-layers similar to the layers in the wurtzite-type structure of ZnS. These nets are separated from each other by the praseodymium atoms. The praseodymium and cadmium atoms form close-packed layers of the stacking sequence (hccc)2 corresponding to the atomic layers (CdCdPrCd)2. The phosphorus atoms occupy octahedral and trigonal bipyramidal voids of the kind Pr3Cd3 and Cd5, respectively. Chemical bonding is briefly discussed. The praseodymium and cadmium atoms obtain their usual oxidation numbers corresponding to the formula Pr3+(Cd2+)3(P3−)3.

Szilard-Chalmers reaction in praseodymium compounds

The β-emitting isotope142gPr (T1/2=19.13 h, E(β)max=2.16 MeV) is a suitable radionuclide for internal radiotherapy with tumor-seeking biomolecules.142gPr can be prepared from natural141Pr by irradiation with thermal neutrons. We investigated the Szilard-Chalmers reaction in well-defined complexes with various ligands and a salt in order to measure the enrichment factors and extracted yields to find a route for the production142gPr of high specific radioactivity, ionic142gPr3+ was separated from the complex by cation exchange and high performance liquid chromatography (HPLC).

Lanthanide trifluoromethanesulfonate complexes with ε‐caprolactam: Synthesis, characterization and structure of the praseodymium compound

Complexes of formulas [Ln(e-cl)8] (F3C-SO3)3 (Ln = La-Eu) and [Ln(ε‐cl)7] (F3C-SO3)3 (Ln = Gd, Tb, Dy, Yb, Lu, ε‐cl = ε‐caprolactam) were synthesized and characterized by elemental analysis, infrared spectroscopy, visible absorption spectroscopy of the Nd compound and emission spectroscopy of the Eu compound and the Gd compound, doped with Eu. IR experimental data suggest that the e-caprolactams are bonded to the central ions through the carbonyl oxygen and that the anions are not coordinated. The parameters calculated from the visible absorption spectrum of the Nd compound suggest electrostatic metal-ligand bonds. The emission spectrum of the europium compound suggests a D2d distorted towards C2v symmetry. X-ray single crystal analysis of the Pr compound shows that the anions are not coordinated and that the coordination polyhedron around the Pr3+ion has a slightly distorted D2d (dodecahedral) symmetry.

The synthesis and structural and physical characterization of a new family of rare-earth metal chalcoantimonates(III): K2(RE)2-xSb4+xSb4Se12, RE= La, Ce, Pr and Gd.

A family of rare-earth metal selenoantimonates(III) has been prepared by the reaction of the elements in alkali metal polyselenide fluxes or by the metathesis of rare-earth chlorides and alkali metal chalcoantimonates(III). The products are black, fine needles of K2(RE)2−xSb4+[itxSe12 where RE=La, Ce, Pr, and Gd and x~0.33. The compounds were analyzed by single crystal and powder X-ray diffraction, and the praseodymium compound by diffuse reflectance spectroscopy, and magnetic susceptibility. The structure, optical spectrum, and susceptibility data of the praseodymium compound are reported.

Formation of New Compounds Ln4Al2O9 in the Ln2O3.Al2O3 System (Ln = La, Pr, Tb)

The new compounds La4Al2O9, Pr4Al2O9, and Tb4Al2O9 were identified in the system 2Ln2O3.Al2O3. X‐ray powder diffraction showed that they were isomorphous with the previously characterized Ln4Al2O9 (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Y) and Ln4Ga2O9 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd). La4Al2O9: P21/c, a = 7.97 Å, b = 11.09 Å, c = 11.41 Å, β= 108.8°, Z = 4; Pr4Al2O9: P21/c, a = 7.80 Å, b = 11.03 Å, c = 11.31 Å, β= 109.6, Z = 4; and Tb4Al2O9: P21c, a= 7.40 Å, b= 10.58 Å, c = 11.16 Å, β= 107.2°, Z = 4. The lanthanum and praseodymium compounds were metastable phases in the Ln4Al2O9 systems and transformed into LaAlO3 and La2O3, and PrAlO3 and PrO1.83 upon prolonged heating at 1200°C, respectively. Ln4Al209 (Ln = La, Pr) were synthesized by precipitation of A1(OH)4−with Ln3+(aq) and subsequent heating at 900°C for 10 h. Tb4AI2O9 required calcination at 1200°C for 10 h. The formation of La4Al2O9 and Pr4Al2O9 was followed by TGA‐DSC, which was also used to assess their thermal stability. Several other members of the above family of compounds were similarly synthesized by the new synthesis route. Particularly, for Nd4Al2O9 this represented a significantly improved method.

ChemInform Abstract: Interstitially‐Stabilized Praseodymium(III) Compounds Na2Pr4Br9NO and Pr8Br13N3O: Structures on the Border Between Salts and Clusters.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Interstitially-Stabilized Praseodymium(III) Compounds Na2Pr4Br9NO and Pr8Br13N3O: Structures on the Border Between Salts and Clusters

Interstitially-Stabilized Praseodymium(III) Compounds Na2Pr4Br9NO and Pr8Br13N3O: Structures on the Border Between Salts and Clusters

The Structure and Magnetic Properties of Pr 3MO7 with M = Nb, Ta, and Sb

The crystal structure of the fluorite-related praseodymium compounds with the composition Pr 3 MO 7, M = Nb, Ta, and Sb, have been determined using Rietveld refinement from X-ray and neutron powder diffraction data at 293 and 4 K. The structure described is orthorhombic with space group Cmcm (No. 63). It is a superstructure of the cubic fluorite structure with unit cell parameters a orth ≈ 2a c, b orth ≈ c orth ≈ a c 2 , as in La 3NbO 7. This structure consists of chains of corner linked MO 6 octahedra parallel with the c-axis. The magnetic susceptibility was measured between 4 and 300 K. The compounds obey the Curie-Weiss law including a Van Vleck temperature independent term. Pr 3SbO 7 shows a small deviation from this law below 25 K.

Crystal and magnetic structures of the permanent magnet material R 2Fe 14C 0.95B 0.05 (RCe, Pr)

Investigations of the compounds R 2Fe 14C 0.95B 0.05 (RCe, Pr) by means of X-ray and neutron diffraction as well as by metallographic techniques and differential thermal analysis (DTA) were carried out. Both compounds crystallize in the tetragonal space group P4 2/ mnm and are isotypic to Nd 2Fe 14B. Lattice constants at 295 K are a = 8.7579(3) A ̊ , c = 11.8867(8) A ̊ , for Ce 2Fe 14C 0.95B 0.05 and a = 8.8138(5) A ̊ , c = 12.0541(15) A ̊ for Pr 2Fe 14C 0.05B 0.05. The samples contained no additional phases except for metallic iron because of the small amount of boron. The nuclear and magnetic structures of the two compounds were investigated by means of neutron diffraction at 643 K (above the Curie temperature T c), at room temperature and below 25 K. For Ce 2Fe 14C 0.95B 0.05 an additional measurement at 423 K was carried out. The magnetic moments of the iron atoms are oriented parallel to the c axis for both compounds. Only small magnetic moments of the rare earth atoms were observed at 12 K for the cerium compound. For the praseodymium compound the magnetic moments of the praseodymium atoms lie parallel to those of the iron atoms. DTA measurements yield a T c value of 347 K for the cerium compound and 520 K for the praseodymium compound. A pronounced change in the specific heat capacity was measured at 515 K for the cerium compound.

In search of chemical clues: Single-crystal structural studies of PrBa 2Cu 3O 6 and PrBa 2Cu 3O 7

Complete refinements of single-crystal X-ray diffraction intensity data for two tetragonal PrBa 2Cu 3O 6 crystals and for two detwinned orthorhombic PrBa 2Cu 3O 7 crystals, along with a more precise refinement for YBa 2Cu 3O 6, have confirmed that the praseodymium compounds are strictly isostructural with the yttrium congeners. Crystallographic data available for the superconducting orthorhombic RBa 2Cu 3O 7 analogs (R=Y, rare earth) were used to establish overall structural trends as a function of lanthanide size. In comparison with these trends, the present results obtained for orthorhombic PrBa 2Cu 3O 7 indicate no markedly unusual structural features; the crystallographic behavior of Pr corresponds to that of the trivalent ion. However, subtle structural anomalies in the PrBa 2Cu 3O x system were revealed by detailed comparisons of structural trends in RBa 2Cu 3O x systems as a function of oxygen content. The axial CuO bond distance is unusually short in both PrBa 2Cu 3O 6 and PrBa 2Cu 3O 7, indicating stronger chemical linkage of the chains and planes as compared to the superconducting systems. Trends in the bond-valence sums and polyhedral volumes about R 3+ suggest that in PrBa 2Cu 3O 7 the increased spatial extension of the 4f-orbitals (as compared to neighboring Nd 3+) mediates strong interactions with the CuO manifold that are capable of inhibiting superconductivity. The retention of superconductivity in Pr 1.85Ce 0.15CuO 4 may arise from significant crystal-chemical differences between the T′ — and the YBa 2Cu 3O 7-type structures: the T′ structure features (1) oxygen layers that are bonded only to Pr, not Cu, and (2) a larger R 3+ polyhedral volume that results in greater isolation of the 4f-orbitals.

Second law assessment of behavior differences in formation of several sulfur-oxygen compounds of lanthanum, cerium, and praseodymium

Normalized experimental data for disproportionation and concomitant I 2 (g) oxidation of SO 3 2- (cr) at 675-775 K in dehydrated Ce 2 (SO 3 ) 2 SO 4 .4H 2 O(cr), admixed with CeO 2 (cr) substrate, were used to evaluate chronological changes and differences in Gibbs energy, enthalpy, and entropy of formation for several product compounds. Several sequential reactions not observed previously were quantified

Raman spectroscopy of some {M}Ba2Cu3O7-δ “cocktails”

Abstract Raman spectra of {M}Ba2Cu3O7-δ ceramics, where {M} stands for two “cocktails” of Y and different rare earth elements, are presented, the composition of mixtures {M} simulating “pseudo” rare earths with ionic radii very close to those of gadolinium and praseodymium. The lattice dynamics of the solid solutions are not driven only by the pseudo rare earth ionic radius since one- and multimode behaviour are found to coexist in the same mixed compound. Substitutional disorder is shown to play a minor role in ceramics, compared to proper effects related to grain boundaries or oxygen vacancies. Finally, the low frequency mode associated to Ba motion is proposed as a fingerprint of the superconducting 1-2-3 phase on account of a comparative study of the true and the pseudo praseodymium compounds.

Crystal field effect and paramagnetic susceptibility of rare earth antimonates Ln 3Sb 5O 12

A new series of rare earth antimonates have been recently synthesized. They have a cubic space group and the symmetry of the rare earth point site is S 4. The absorption and emission spectra of pure and doped europium and praseodymium compounds are reported. Free ion and crystal field parameters are deduced. From the derived wavefunctions, the thermal evolution of the paramagnetic susceptibility is calculated and is in good agreement with the experiment.

ChemInform Abstract: Nitrate Complex Compounds of Praseodymium.

AbstractThe novel title compounds MPr(NO3)5·nH2O (M: Mg; n = 11 and M: Ca, Ba; n = 10) are prepared according to a known procedure.