Hydrothermal phase equilibria in Ln2O3-H2O systems

Hydrothermal phase equilibria studies have been carried out in the Ln₂O₃-H₂O systems (Ln = La, Pr, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and the stability fields of the phases Ln(OH)₃ LnOOH and Ln₂O₃-C have been established in the pressure-temperature range of 25000 psi and 900° C. The sequioxides Ln₂O₃-C are stable only in the last four systems of Er to Lu along with the Ln(OH)₃ and LnOOH. The systems from Nd to Ho have only Ln(OH)₃ and LnOOH as stable phases and those from La to Pr have only Ln(OH)₃ as the stable phase. The unit cell parameters of trihydroxides deviate from the values reported in the literature and this is attributed to the contamination of CO₂ in the starting material.     

Thermodynamic properties of nonsuperconducting Ln2CuO4 (Ln = Nd, Sm, Eu), Ho2Cu2O5 and Ln2BaCuO5 (Ln = Nd, Sm, Eu, Ho, Yb) cuprates

Thermodynamic properties of rare-earth Ln₂CuO₄ (Ln = Nd, Sm, Eu), Ho₂Cu₂O₅ and Ln₂BaCuO₅ (Ln = Nd, Sm, Eu, Ho, Yb) cuprates were determined using the electromotive force method with a fluorine-ion electrolyte in the temperature interval of 1000–1230 K. The thermodynamic data obtained by different experimental methods were compared.     

Heteroleptic polypyrazolylborate derivatives of the lanthanide ions. The synthesis of acetylacetonate derivatives and the molecular structures of [Ln{HB(C3N2H3)3}2{MeC(O)CHC(O)Me}] (Ln = Ce,Yb)

The air and moisture stable complexes [Ln{HB(C₃N₂H₃)₃}₂{MeC(O)CHC(O)Me}] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, Lu, Y), have been prepared and characterized. The molecular structures of the compounds with Ln = Ce and Yb reveal that a substantial distortion of the coordination geometry found for Ce³⁺ is necessary to allow the ligand set to accommodate the smaller Yb³⁺ ion.     

Structural features of thiocarbamide derivatives of some lanthanide iodides

Data on the synthesis, IR spectroscopy, and single crystal XRD are presented for thiocarbamide compounds of the composition [Ln(H₂O)₉]I₃·2CS(NH₂)₂, where Ln = Dy (I) and Yb (II). The structural features of [Ln(H₂O)₉]I₃·2CS(NH₂)₂ (Ln = Pr, Nd, Eu, Gd, Dy, Ho, Er, and Yb) are discussed. The compounds of thiocarbamide with Pr, Nd, Eu, Gd, and Dy iodides are found to form the first isostructural series characterized by a continuous network structure, while with Ho, Er, and Yb iodides the second isostructural series with a layered type structure is formed.     

Lumineszenz und sensibilisierte Emission der dreiwertigen Seltenen Erden in Sr3La2W2O12

By activation of the new host lattice Sr₃La₂W₂O₁₂ with the trivalent rare earth ions Nd, Eu, Ho, Er, Tm, Yb an intense emission in the visible and/or infrared region is obtained. Energy transfer from Er³⁺ to Tm³⁺ and Nd³⁺ to Yb³⁺ has been found to occur. The excitation, emission, and diffuse reflectance spectra are analyzed for Sr₃La₂W₂O₁₂: Ln³⁺ (Ln = Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb).     

Studies on some ternary oxyborates of the Na2O-Me2O3-B2O3 (Me=rare earth or aluminum) systems: Synthesis, structure and crystal growth

Sodium rare-earth oxyborates Na₂RE₂O(BO₃)₂ (RE=Y, Nd, Er) were prepared for the first time in the present study. They were found to be isostructural with phases of the same composition containing Sm, Eu or Gd and reported by Corbel et al. [J. Solid State Chem.144 (1999) 35-44]. It was shown that the yttrium and erbium compounds could be synthesized at 900-1000 °C by a solid-state reaction between oxides in an equimolecular ratio. With both oxyborates melting led to decomposition into a mixture of Y(Er)BO₃, Y₂(Er₂)O₃ and Na₂B₄O₇. Just the opposite was observed during thermal treatment of the oxide mixture containing Nd₂O₃, from which a practically pure phase of Na₂Nd₂O(BO₃)₂ was only obtained after melting. The attempts to synthesize the oxyborate Na₂La₂O(BO₃)₂ showed it to be unstable, this leading to the formation of a mixture containing, in addition to Na₂La₂O(BO₃)₂, also other already known stable phases of the system Na₂O-La₂O₃-B₂O₃ along with an unknown ternary oxide phase. This phase was found to represent a new oxyborate of sodium and lanthanum with the formula Na₃La₉O₃(BO₃)₈, whose single crystals were obtained by flux growth. It was established that synthesis of a polycrystalline material with the same composition was also possible using solid-state interaction between Na₂CO₃, La₂O₃ and H₃BO₃ at 1000-1100 °C. X-ray diffraction experiments on single crystals were used to solve the structure of Na₃La₉O₃(BO₃)₈. The unit cell was found to be hexagonal, space group P62m (No. 189) with Z=1. The compound can be regarded as the forefather of a second group of oxyborates representing a new family of isostructural compounds, Na₃RE₉O₃(BO₃)₈. Such phases were obtained with RE=Nd, Sm and Eu whereas with RE=Y and Gd, the synthesis experiments failed.The concentration and temperature regions of crystallization of the double-oxyborate Na₂Al₂O(BO₃)₂ in the ternary system Na₂O-Al₂O₃-B₂O₃ were determined. This compound was shown to melt incongruently at 970±3 °C, which made high-temperature solution growth most appropriate for obtaining its single crystals with NaBO₂ as the best solvent. On the basis of the data obtained, a composition of the initial solution was proposed, the validity of the choice being demonstrated by the growth of Na₂Al₂O(BO₃)₂ single crystals on a seed using the top-seeded solution growth (TSSG) technique and slow cooling of the solution.     

Synthesis,Structures, and Luminescent Properties of Chloride and Nitrate LnIII Complexes Coordinated by tris(Pyrazolyl)methane

We report the synthesis of Ln³⁺ nitrate [Ln(Tpm)(NO₃)₃] ⋅ MeCN (Ln=Yb ( 1Yb ), Eu ( 1Eu )) and chloride [Yb(Tpm)Cl₃] ⋅ 2MeCN ( 2Yb ), [Eu(Tpm)Cl₂(μ-Cl)]₂ ( 2Eu ) complexes coordinated by neutral tripodal tris(3,5-dimethylpyrazolyl)methane (Tpm). The crystal structures of 1Ln and 2Ln were established by single crystal X-ray diffraction, while for 1Yb high resolution experiment was performed. Nitrate complexes 1Ln are isomorphous and both adopt mononuclear structure. Chloride 2Yb is monomeric, while Eu³⁺ analogue 2Eu adopts a binuclear structure due to two μ²-bridging chloride ligands. The typical lanthanide luminescence was observed for europium complexes ( 1Eu and 2Eu ) as well as for terbium and dysprosium analogues ([Ln(Tpm)(NO₃)₃] ⋅ MeCN, Ln=Tb ( 1Tb ), Dy ( 1Dy ); [Ln(Tpm)Cl₃] ⋅ 2MeCN, Ln=Tb ( 2Tb ), Dy ( 2Dy )).     

Concentration quenching of the Nd3+ emission in alkali rare earth borates

Four new ternary compounds with compositions Li₆Nd(BO₃)₃, Na₃Nd(BO₃)₂, and Na₁₈Nd(BO₃)₇ have been found in the M₂ONd₂O₃B₂O₃ systems, where M is either Li or Na. Concentration quenching of the neodymium emission in homologous lanthanum or gadolinium borates has been investigated. While in the Li₆Gd(BO₃)₃, Na₃La₂(BO₃)₃, and Na₃La(BO₃)₂ host lattices the quenching rate shows a quadratic dependence on Nd³⁺ concentration, as expected since the coordination polyhedra are connected by common faces or edges, in Na₁₈La(BO₃)₇ the luminescent lifetime is not influenced by neodymium concentration. Lifetimes and crystal field splitting of the J levels are compared to those of other oxide host lattices.     

The Ternary System Li2O-Al2O3-B2O3: Compounds and Phase Relations

The ternary system Li₂O-Al₂O₃-B₂O₃ is reinvestigated with solid-state reaction and X-ray powder diffraction technique to clarify some long-standing uncertainties. The phase relations are constructed based on the phase identifications of 51 ternary samples. Six ternary compounds, Li₂AlB₅O₁₀, LiAlB₂O₅, Li₃AlB₂O₆, Li₂AlBO₄, LiAl₇B₄O₁₇ and a compound with a composition close to 0.66Li₂O·0.06Al₂O₃·0.28B₂O₃, are observed or confirmed in this system, and the thermal stability of these ternary compounds is also discussed on the basis of DTA experimental results.     

Molar enthalpies of formation of LnAl2 compounds

The enthalpy of solution of Eu in Al and the standard molar enthalpy of formation of LnAl₂ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) were determined by dissolution calorimetry, using a calorimeter based on liquid aluminium. Experimental results are compared with model predictions.     

Lanthanide perchlorate complexes of 4-cyano pyridine-N-oxide, 4-chloro 2-picoline-N-oxide and 4-dimethyl amino-2-picoline-N-oxide

Complexes of lanthanide perchlorates with 4-cyano pyridine-1-oxide, 4-chloro 2-picoline-1-oxide and 4-dimethyl-amino 2-picoline-1-oxide have been isolated for the first time and characterized by analysis, conductance, infrared, NMR and electronic spectra. The complexes of 4-cyano pyridine-1-oxides have the composition Ln(CyPO)₆(ClO₄)₃. 2H₂O (Ln=La, Sm, Dy and Ho); Ln(CyPO)₇ (ClO₄)₃. 2H₂O (Ln=Pr, Nd, Er and Yb); and Ln(CyPO)₅ (ClO₄)₃. 2H₂O (Ln=Gd and Tb). The complexes of 4-chloro 2-picoline-1-oxide analyse for the formulae Ln(CpicO)₆ (ClO₄)₃ (Ln=La, Pr, Nd and Ho); and Ln (CpicO)₅ (ClO₄)₃ (Ln=Er and Yb), and those of 4-dimethylamino 2-picoline-1-oxide for Ln(DMPicO)₆ (ClO₄)₃ (Ln=La and Nd); Ln(DMPicO)₇ (ClO₄)₃ (Ln=Gd, Er and Yb); and Ln(DMPicO)₈ (ClO₄)₃ (Ln=Dy and Ho).     

Synthesis of rhombohedral borates Ba3R(BO3)3, R = Pr-Dy

Compounds with the composition Ba₃R(BO₃)₃ (R = Pr, Nd, Sm, Eu, Gd, Tb, Dy) were obtained by solid-phase reactions at 1000°C. The compounds were studied by the methods of IR spectroscopy and X-ray and differential thermal analyses. Physicochemical properties of some of them were determined.     

2,2′‐Bipyrimidine as Efficient Sensitizer of the Solid‐State Luminescence of Lanthanide and Uranyl Ions from Visible to Near‐Infrared

Treatment of Ln(NO₃)₃?nH₂O with 1 or 2 equiv 2,2′‐bipyrimidine (BPM) in dry THF readily afforded the monometallic complexes [Ln(NO₃)₃(bpm)₂] (Ln=Eu, Gd, Dy, Tm) or [Ln(NO₃)₃(bpm)₂]?THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln=Ce, Nd, Sm) yielded one of two distinct monometallic complexes, depending on the recrystallization solvent: [Ln(NO₃)₃(bpm)₂]?THF (Ln=Nd, Sm) from THF, or [Ln(NO₃)₃(bpm)(MeOH)₂]?MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO₂(NO₃)₂?6H₂O with 1 equiv BPM in THF afforded the monoadduct [UO₂(NO₃)₂(bpm)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid‐state luminescence measurements on these monometallic complexes showed that BPM is an efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the Yb^III ion emitting in the near‐IR. For Tb, Dy, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8 %, respectively. All these complexes in the solid state were stable in air.     

Phonon modes of A(Co1/2Mn1/2) O3 (A=La, Nd, Dy, Ho, Yb)

Phonon energies in cobaltite/manganites A(Co_1/2Mn_1/2)O₃, where A is a lanthanide, have been determined by far-infrared spectroscopy. The phonon energies systematically shift and split and new modes appear as the mass of the lanthanide is increased through the series A=La, Nd, Dy, Ho, Yb. The behavior of the phonon modes correlates with the magnetic properties of this series of compounds, in particular with the appearance of metamagnetism for the compounds with smaller ions on the A site.     

On the Perovskites Ba2LnSbO6 (Ln = Nd,Sm, Eu,Gd, Tb,Dy, Ho,Er, Yb)

Polycrystalline Ba₂LnSbO₆ (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) are cubic, perovskite-type compounds, space group Fm3m (No. 225), Z = 4, with a values from a = 8.544(2) Å for Ba₂NdSbO₆ to a = 8.368(1) Å for Ba₂YbSbO₆. X-ray diffraction data for all the compounds and the results of magnetic measurements for two of them are given.     

Synthesis and structural study of the new rare earth magnesium borates LnMgB5O10 (Ln = La, …, Er)

To obtain rare earth luminescent materials with weak concentration quenching, the B₂O₃-rich portion of the ternary diagram Ln₂O₃MgOB₂O₃ (Ln = rare earth) has been investigated. A ternary phase of composition LnMgB₅O₁₀ has been found for Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er. These compounds all crystallize in the monoclinic space group $\text{P2}{}_1\text{c}$. The structure has been determined on a LaMgB₅O₁₀ crystal. A full-matrix least-squares refinement leads to R = 0.039. The structure can be described as being made of (B₅O₁₀^5?)_n two-dimensional layers linked together by the lanthanum and magnesium ions. The rare earth atom coordination polyhedra form isolated chains. These borates are isostructural with some rare earth cobalt borates.     

Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Ln₂(C₇H₁₀O₄)₃.nH₂O (wheren=16 in the case of La, Ce, Pr, Nd and Sm pimelates,n=8 for Eu, Gd, Tb, Dy, Er and Tm pimelates,n=12 for Ho, Yb and Lu pimelates) were also reported.

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Zusammenfassung Mittels TG, DTG, DTA wurde in Verbindung mit IR-Methoden der mehrstufige Dehydratations- und der Zersetzungsvorgang der Polyhydrate der PimelinsÄuresalze von dreiwertigem Lanthan und dreiwertigen Lanthanoiden untersucht. Röntgendiffraktionsdaten der untersuchten Heptandiat-Komplexe mit der allgemeinen Formel Ln₂(C₇H₁₀O₄)₃ nH₂O (mitn=16 für Ln=La, Ce, Pr, Nd und Sm,n=8 für Ln=Eu, Gd, Tb, Dy, Er und Tm sowien=12 für Ln=Ho, Yb und Lu) werden ebenfalls gegeben.

     

Syntheses, structure and rare earth metal photoluminescence of new and known isostructural A2Mo4Sb2O18 (A=Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) compounds

Nine new A₂Mo₄Sb₂O₁₈ (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds have been synthesized by solid-state reactions. They are isostructural with six reported analogues of yttrium and other lanthanides and the monoclinic unit cell parameters of all fifteen of them vary linearly with the size of A³⁺ ion. Single crystal X-ray structures of eight A₂Mo₄Sb₂O₁₈ (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds have been determined. Neat A₂Mo₄Sb₂O₁₈ (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit characteristic rare earth metal photoluminescence.     

4-Nitro and 4-chloro pyridine-N-oxide complexes of lanthanide perchlorates

Adducts of lanthanide perchlorates with 4-nitro and 4-chloro pyridine-Noxides (4-NPNO and 4-CPNO respectively) have been synthesised for the first time and characterised by analysis, electrolytic conductance, infrared, proton-NMR and electronic spectral data. The complexes are of the compositions Ln₂(NPNO)₁₅ (ClO₄)₆ (Ln = La, Pr, Nd and Gd), Tb(NPNO), (C1O₄)₆), Ln₂(NPNO)₁₃ (C1O₄)₆) (Ln = Dy, Ho, and Yb); Ln (CPNO)₈ (C10₄)₃) (Ln = La, Pr, Nd, Tb, Dy, Ho and Yb) and Ln(CPNO), (C1O₄)₃) (Ln = Sm and Gd). Conductivity and IR data provide evidence for the non-coordinated nature of the perchlorate groups. IR and NMR spectra suggest coordinationvia the oxygen of the N-oxide group. Electronic spectral shapes of the Nd⁺³ and Ho⁺³ complexes are interpreted in terms of eight-and seven-coordinate environments in the case of 4-NPNO complexes and eight-coordination in the case of 4-CPNO complexes. IR data indicate bridged structure in NPNO complexes of lanthanides other than Tb.     

Synthesis and powder X-ray diffraction analysis of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl

A series of new mixed rare-earth and selenium oxychlorides with composition LnSeO₃Cl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Y) were prepared by annealing together LnOCl and SeO₂ in sealed silica tubes. The resulting compounds were characterized by powder X-ray diffraction. The unit cell parameters of the phases were determined. Lanthanum—europium oxychlorides crystallized in the tetragonal system to give the Sillen phases analogously to tellurium compounds with the similar formula, whereas Tb—Yb and Y oxychlorides crystallized in the orthorhombic system. It is likely that the latter oxychlorides are not layered compounds.