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Rare earth (Er3+ and Nd3+) ions doped cadmium lithium boro tellurite (CLiBT) glasses were prepared by melt quenching method. The vis–NIR absorption spectra of these glasses have been analyzed systematically. Judd–Ofelt intensity parameters Ωλ (λ = 2, 4, 6) have been evaluated and used to compute the radiative properties of emission transitions of Er3+ and Nd3+: CLiBT glasses. From the NIR emission spectra of Er3+: CLiBT glasses a broad emission band centered at 1538 nm (4I13/2 → 4I15/2) is observed and from Nd3+: CLiBT glasses, three NIR emission bands at 898 nm (4F3/2 → 4I9/2), 1070 nm (4F3/2 → 4I11/2) and 1338 nm (4F3/2 → 4I13/2) are observed with an excitation wavelength λexci = 514.5 nm (Ar+ Laser). The FWHM and stimulated emission cross-section values are calculated for Er3+ and Nd3+: CLiBT glasses. FWHM × σeP values are also calculated for Er3+: CLiBT glasses. 相似文献
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Systematic phase analytical studies of the systems RE-Ir-X (X = Sn, Pb, Sb, Bi) led to 15 new stannides, plumbides, antimonides and bismuthides with the composition RE5Ir2X. The compounds have been synthesized and characterized by X-ray powder diffraction. The structures of Gd5Ir2Sb and Dy5Ir2Bi have been refined from single crystal X-ray diffractometer data: Mo5SiB2 type, I4/mcm, a = 775.2(2), c = 1361.3(5) pm, wR2 = 0.0933, 404 F2 values, 16 variables for Gd5Ir2Sb and a = 767.5(1), c = 1368.9(3) pm, wR2 = 0.0694, 571 F2 values, 16 variables for Dy5Ir2Bi. Magnetic measurements of Gd5Ir2X (X = Sn, Pb, Sb, Bi), Tb5Ir2X (X = Sn, Pb, Sb, Bi), Dy5Ir2Pb, Dy5Ir2Bi and Ho5Ir2Pb indicate ferromagnetic transitions at TC = 154.3, 159.3, 124.4, 119.3, 99.2, 98.2, 65.5, 68.6, 45.1, 35.6 and 23.5 K, respectively. Gd5Ir2Bi and Gd5Ir2Sb show an additional antiferromagnetic transition at TN = 118.5 and 91.0 K. The magnetocaloric effect of Gd5Ir2X (X = Sn, Pb, Sb, Bi) in terms of the isothermal entropy change ΔSm is −7.3(3), –6.5(3), –8.7(3) and −9.0(3) J kg−1 K−1 at temperatures of 153, 157, 120 and 126 K for a 5 T field change. 119Sn Mössbauer spectra of Gd5Ir2Sn at 78 K show a huge transferred hyperfine field of 21.9(1) T and an isomer shift of 1.94(1) mm s−1, typical for stannides. 121Sb Mössbauer spectra of Gd5Ir2Sb at 78 K show a transferred hyperfine field of 14.2(3) T and an isomer shift of −7.45(8) mm s−1 reflecting the antimonide character. 相似文献
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The TiNiSi type intermetallic compounds RERhZn (RE = Y, Sm, Gd–Lu) were synthesized by induction melting of the elements in sealed tantalum ampoules. They were characterized by X-ray powder diffraction. Five structures were refined from single crystal X-ray diffractometer data: Pnma, Z = 4, a = 699.7(2), b = 405.6(2), c = 816.9(2) pm, wR2 = 0.038, 628 F2 values for SmRhZn, a = 696.1(2), b = 405.6(1), c = 811.9(3) pm, wR2 = 0.028, 886 F2 values for GdRhZn, a = 692.8(1), b = 403.0(1), c = 809.5(2) pm, wR2 = 0.039, 562 F2 values, for TbRhZn, a = 690.6(3), b = 401.50(9), c = 808.2(2) pm, wR2 = 0.036, 763 F2 values, for DyRhZn, and a = 688.6(5), b = 399.6(4), c = 808.3(7) pm, wR2 = 0.048, 546 F2 values for HoRhZn with 20 variables for each refinement. The rhodium atoms have coordination number 9 (5 RE + 4 Zn atoms) in the form of a tricapped trigonal prism. Together the rhodium and zinc atoms build up three-dimensional [RhZn] networks with short Rh–Zn (263–269 pm in GdRhZn) and Zn–Zn (296 pm in GdRhZn) distances. The gadolinium atoms bind to the [RhZn] network by Gd–Rh bonds (292–294 pm). Magnetic susceptibility measurements show Pauli paramagnetism for YRhZn and van Vleck paramagnetism for SmRhZn. The remaining RERhZn compounds are Curie–Weiss paramagnets which show magnetic ordering at low temperatures. 相似文献
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The preparation of BaCeO3 doped by gadolinium, europium, and terbium oxides (BaCe0.8Eu0.1Tb0.1O2.9 and BaCe0.8Gd0.2O2.9) has been performed by solid-state reaction from BaCO3, CeO2, Gd2O3, Eu2O3, Tb4O7. The X-ray measurements have showed that BaCe0.8RE0.2O2.9 (RE = Gd, Eu, Tb) was orthorhombic structure (space group Pnma). The standard formation enthalpies of BaCe0.8Eu0.1Tb0.1O2.9 and BaCe0.8Gd0.2O2.9 have been determined by solution calorimetry combining the solution enthalpies of BaCe0.8Gd0.2O2.9 (BaCe0.8Eu0.1Tb0.1O2.9) and BaCl2 + 0.8CeCl3 + 0.2GdCl3 (BaCl2 + 0.8CeCl3 + 0.1EuCl3 + 0.1TbCl3) mixtures in 1 M HCl with 0.1 M KI at T = 298.15 K and literature data. 相似文献
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The metallic ferromagnetic perovskite-type SrRuO3 (TC ~ 160 K) belongs to the “class” of materials with strongly correlated electrons. Nonetheless a simple ferromagnetism associated with isotropic interactions of low spin Ru4+ ions local moments is far too simple to explain the complex interplay between charge carriers and magnetic interactions. In that sense the suppression of ferromagnetism in isoelectronic Sr1?xCaxRuO3 was tentatively associated to the increased lattice distortion influencing primarily the 4d Ru bandwidths and, hence, the itinerancy and respective populations of the spin-up and spin-down electrons.In order to probe the robustness of the metallic ferromagnetism against electron occupation of 4d Ru orbital we prepared and characterized polycrystalline Sr1?xNaxRuO3 (x = 0.0–0.19) ceramics. The substitution of Sr2+ by Na1+, leading to formally mixed valence Ru4+/Ru5+, induces the decrease of the Curie temperature and spin-wave stiffness, which was determined independently from magnetic and specific heat data. On the other hand the effective paramagnetic moment remains essentially unchanged. All compounds are metallic in a sense of electrical resistivity and thermopower temperature dependence; the low temperature upturn of the electrical resistivity was explained on a base of the weak localization. The metallic nature of the samples is corroborated by Pauli paramagnetism and high Sommerfeld coefficient γ, extracted from the low temperature specific heat, which increases from 30.9 mJ mol?1 K?2 (x = 0.0) to 43.0 mJ mol?1 K?2 (x = 0.19). 相似文献
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Synthesis, crystal structures and magnetic properties of metal telluromolybdates MxM′1?xTeMoO6 (M, M′ = Mn, Co, Cd) have been investigated. Their crystal structures have two-dimensional arrays of M and M′ atoms. From the powder X-ray diffraction measurements, MnxCo1?xTeMoO6 adopt an orthorhombic structure throughout the composition range (x = 0.0–1.0). On the other hand, MnxCd1?xTeMoO6 and CoxCd1?xTeMoO6 adopt two types of structures corresponding to their end members (orthorhombic for Mn- or Co-rich solid solutions; tetragonal for Cd-rich ones). In the intermediate compositions, it was found that two phases coexist with different metal components. Magnetic properties of these solid solutions were investigated. All the MnxCo1?xTeMoO6 exhibits an antiferromagnetic transition at ~23 K. The antiferromagnetic transition was also observed in MnxCd1?xTeMoO6 and CoxCd1?xTeMoO6. However, the Néel temperature rapidly decreases with increasing the concentration of Cd and disappeared below x = 0.6, which is characteristic for two-dimensional magnetic system. 相似文献
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In this research two competing phenomena, back bonding and hyperconjugation, have been investigated based on Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) analyses for radical AH3?nXn species, where A = Si and Ge, and n = 1, 2 and 3. It is demonstrated in this article that both above phenomena will be occurred significantly, while back bonding is the only event in analogous compounds with carbon and hyperconjugation is rather negligible. It was also found that only one back bonding with the help of keyword $CHOOSE in NBO analysis can be found in this type of compounds with reasonable structure, while it can be sometimes detected in AH3?nXn without using keyword $CHOOSE. It is also shown that there is always an increase in bond length in comparison with reference molecules in mentioned species due to existing hyperconjugation, while if the central atom is carbon, we have always a decrease of bond length due to only having back bonding. Additionally, from AIM point of view, the delocalization indices for α-spin (majority spin) is more than β-spin (minority spin) in radical species for molecules without back bonding, while the situation in our compounds is quite reverse, which can be attributed to the π back bonding in the β-spin electrons. 相似文献
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《The Journal of chemical thermodynamics》2004,36(11):925-928
New compounds of aspartic acid Cs(ASP) · nH2O (n = 0, 1) have been synthesized and characterized by XRD, IR and Raman spectroscopy as well as TG. The structural formula of this new compound was Cs(ASP) · nH2O (n = 0, 1). The enthalpy of solution of Cs(ASP) · nH2O (n = 0, 1) in water were determined. With the incorporation of the standard molar enthalpies of formation of CsOH(aq) and ASP(s), the standard molar enthalpy of formation of −(1202.9 ± 0.2) kJ · mol−1 of Cs(ASP) and −(1490.7 ± 0.2) kJ · mol−1 of Cs(ASP) · H2O were obtained. 相似文献
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Evans O. Changamu Holger B. Friedrich 《Journal of organometallic chemistry》2008,693(21-22):3351-3356
The halogenoalkyl complexes [Cp(CO)2M{(CH2)nX}] (n = 3–10, 12, M = Fe; n = 5, 6, M = Ru, X = Br, I) react with Ph3CPF6 in dry CH2Cl2 to give the corresponding carbocation complexes [Cp(CO)2M{η2-(CH2CH(CH2)n?2X}]PF6 in high yields. NMR evidence indicates that the metals form metallacyclopropane type structures with the carbocation ligand. The reactions of some of the cationic complexes with NaI, PPh3, Na[Cp(CO)2Fe] and Et3N are discussed. NaI and Na[Cp(CO)2Fe] displace the halogeno-olefin, while PPh3 adds at the β-CHδ+ giving the unstable phosphonium adducts [Cp(CO)2Fe{CH2CH(PPh3)(CH2)n?2X}]PF6 which decompose to the halogeno-olefins and the cationic PPh3 complex [Cp(CO)2Fe(PPh3)]+. Et3N causes allylic deprotonation forming internal olefin complexes of the type [Cp(CO)2Fe{CH2CHCH(CH2)n?3X}]PF6. 相似文献
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A crystallochemical study was undertaken to investigate the structural stability and the compositional extent of the ternary borides M2(Ni21−xMx)B6 (M Ti, Zr, Hf). This phase often occurs during the production of MB2 joints by means of Ni–B brazing alloys. Samples with the nominal compositions M2Ni21B6 and M3Ni20B6 were synthesized by arc melting and characterized by optical and electron microscopy, and X-ray diffraction. Crystal structure refinements were performed by the Rietveld method. The compositional boundaries of the ternary phases were experimentally determined and found strictly related to the M/Ni size ratio. The stability of this structure is mainly determined by the capability of the structure to expand under the effect of the Ni substitution by the M atom. The CALPHAD modeling of the three M–Ni–B ternary systems in the Ni-rich corner of the phase diagram, performed on the basis of the obtained structural data, shows a good agreement with experimental results. 相似文献
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Thermodynamic properties of schapbachite (α-AgBiS2) in the phase assemblage α-AgBiS2–AgBi3S5–Bi have been studied by an EMF-technique. The EMF-measurements were made on the galvanic cell Pt(−)|Ag|AgI|AgBiS2 + AgBi3S5 + Bi|C|Pt(+), over the temperature range from (429 to 699) K. According to the EMF vs. temperature relations obtained, the enthalpy of the phase transformation from β-AgBi1+xS2 to α-AgBi1+xS2, at T = (465.55 ± 5) K, was calculated to be (7.3 ± 2.1) kJ · mol−1. New experimentally determined thermodynamic properties of the bismuth-saturated schapbachite (α-AgBi1+xS2), for each temperature region of the stable phases Bi(s) and Bi(l), were generated and analysed in detail. Based on the experimental results, Gibbs free energies of sulfidation reactions including Ag, Bi(l), S2(g), Ag2S and Bi2S3 to produce the bismuth-saturated schapbachite (α-AgBi1+xS2) have been evaluated. It has been observed that within the temperature range from (474 to 680) K, schapbachite saturated with bismuth (α-AgBi1+xS2) is thermodynamically more stable than the stoichiometric schapbachite (α-AgBiS2). 相似文献
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The (solid + liquid) phase equilibria of the ternary systems (CsBr + LnBr3 + H2O) (Ln = Pr, Nd, Sm) at T = 298.2 K were studied by the isothermal solubility method. The solid phases formed in the systems were determined by the Schreinemakers wet residues technique, and the corresponding phase diagrams were constructed based on the measured data. Each of the phase diagrams, with two invariant points, three univariant curves, and three crystallization regions corresponding to CsBr, Cs2LnBr5·10H2O and LnBr3·nH2O (n = 6, 7), respectively, belongs to the same category. The new solid phase compounds Cs2LnBr5·10H2O are incongruently soluble in water, and they were characterized by chemical analysis, XRD and TG-DTG techniques. The standard molar enthalpies of solution of Cs2PrBr5·10H2O, Cs2NdBr5·10H2O and Cs2SmBr5·10H2O in water were measured to be (52.49 ± 0.48) kJ · mol−1, (49.64 ± 0.49) kJ · mol−1 and (50.17 ± 0.48) kJ · mol−1 by microcalorimetry under the condition of infinite dilution, respectively, and their standard molar enthalpies of formation were determined as being −(4739.7 ± 1.4) kJ · mol−1, −(4728.4 ± 1.4) kJ · mol−1 and −(4724.4 ± 1.4) kJ · mol−1, respectively. The fluorescence excitation and emission spectra of Cs2PrBr5·10H2O, Cs2NdBr5·10H2O and Cs2SmBr5·10H2O were measured. The results show that the upconversion spectra of the three new solid phase compounds all exhibit a peak at 524 nm when excited at 785 nm. 相似文献
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Agnieszka Czylkowska Danuta Czakis-Sulikowska Rafał Kruszyński Mirosława Markiewicz 《Structural chemistry》2010,21(2):415-423
A novel mixed-ligand complexes of Er(III), Yb(III) and Lu(III) with title ligands were prepared and characterized by chemical
and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulphoxide). The thermal
properties of complexes in the solid state were studied. The mode of metal–ligand coordination was discussed. The title compounds
are isomorphic and isostructural in solid state. All atoms in studied compounds lie in general positions but occurrence of
inversion on the midpoint of the bond linking two pyridine rings leads to existence in asymmetric unit one complex molecule
and half of outer coordination sphere 4-bpy molecule. All chelating carboxylate groups are symmetrically bonded to the metal
cations. The molecules of studied compounds are connected to the three dimensional network via O–H···O and O–H···N intermolecular
hydrogen bonds. In the structures also exist C–H···O, C–H···Cl weak hydrogen bonds and π····π stacking interactions. 相似文献