On the boron rich phases in the Yb-B system (original) (raw)
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Synthesis and properties of YbB2
Journal of Alloys and Compounds, 2003
We report temperature and field dependent measurements of the magnetic susceptibility, specific heat and resistivity of sintered YbB 2 pellets, prepared via two distinct reaction routes, utilizing different temperatures, pressures and sintering times. Sample behavior is affected by the preparation procedure, as a consequence of different secondary phases, most of which were identified via x-ray diffraction. These experiments show that YbB 2 is a metal with the Yb atoms in or very close to their 3+ state. YbB 2 appears to order anti-ferromagnetically at T N = 5.6 ± 0.2 K, which can be considered a relatively high ordering temperature for an ytterbium-based intermetallic compound.
Journal of Solid State Chemistry, 2012
ABSTRACT Polycrystalline samples and single crystals of the new complex boride Ti1+xRh2−x+yIr3−yB3 (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B4 fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1) Å, b=14.995(2) Å and c=3.234(1) Å. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron–boron interactions are observed in the trans zigzag B4 fragment, which induce a clear differentiation of two types of metal–boron contacts with different strength. The observed three-dimensional metal–metal interaction is in good agreement with the predicted metallic behavior.
Journal of Alloys and Compounds, 2019
In this work we report the results of our investigation of YbB 66 as a potential high-temperature thermoelectric material. A high-quality single crystal has been grown by the optical floating zone method. Thermoelectric transport properties were measured in a temperature range of 373e973 K YbB 66, like REB 66 compounds in general, is a p-type semiconductor whose electrical properties can be described by Mott's variable range hopping mechanism. It shows very large Seebeck coefficient ranging from 588 mV K À1 at 373 K to 241 mV K À1 at 973 K and an electrical resistivity r that decreases by almost 4 orders of magnitude from 9.4Â10 À1 U m to 2.4 Â 10 À4 U m. Together with the low thermal conductivity of 2.6 W m À1 K À1 a maximum ZT close to 0.1 around 1000 K was determined with trend of sharp increase toward higher temperatures, which is similar to the previous report of SmB 66 , and significantly larger than previously reported for Y and Er phases of REB 66. However, unlike SmB 66 , the effective magnetic moment suggests a trivalent state for Yb instead of mixed valence, which was determined by measuring the magnetic susceptibility from 2 to 300 K. The composition of YbB 66 was indicated to be metal-rich, which actually may be the origin of the good performance.
Zeitschrift für Naturforschung B, 2014
Transparent and colorless single crystals of Yb 26 B 12 O 57 were obtained by reacting Yb 2 O 3 and B powder at 1000 • C in the presence of a KCl flux for 24 h in silica-jacketed Nb ampoules and subsequent removal of the flux by washing with water. Yb 26 B 12 O 57 crystallizes in the monoclinic space group C2/m (no. 12, Z = 1) with the lattice parameters a = 2454.1(3), b = 357.78(4), c = 1426.7(2) pm and β = 115.111(6) • , and its structure differs slightly from that of a known compound with the same stoichiometry. Raman spectra of single crystals of the title compound were recorded and compared to those of known borate compounds.
Ba3Yb(BO3)3 single crystals: Growth and spectroscopic characterization
Journal of Materials Research, 2008
We obtained Ba3Yb(BO3)3 single crystals by the flux method with solutions of the BaB2O4–Na2O–Yb2O3 system. The evolution of the cell parameters with temperature shows a slope change at temperatures near 873 K, which may indicate a phase transition that is not observed by changes appearing in the x-ray powder patterns or by differential thermal analysis (DTA). The evolution of the diffraction patterns with the temperature shows incongruent melting at temperatures higher than 1473 K. DTA indicates that there is incongruent melting and this process is irreversible. Ba3Yb(BO3)3 has a wide transparency window from 247 to 3900 nm. We recorded optical absorption and emission spectra at room and low temperature, and we determined the splitting of Yb3+ ions. We used the reciprocity method to calculate the maximum emission cross section of 0.28 × 10−20 cm2 at 966 nm. The calculated lifetime of Yb3+ in Ba3Yb(BO3)3 is τrad = 2.62 ms, while the measured lifetime is τ = 3.80 ms.
Synthesis and reaction sintering of YB4 ceramics
Ceramics International, 2019
Within this work, the preparation of yttrium tetraboride (YB 4) in the form of powder as well as bulk material was investigated. Powders were synthesized via four different reaction methods, including direct synthesis from elemental powders, reduction of yttrium oxide with boron, boron carbide reduction, and combined boron carbide/carbothermal reduction at 1500°C, 1700°C and 1900°C. Pure YB 4 powder was successfully synthesized using the combined boron carbide/carbothermal reduction method. Secondary phases, especially Y 2 O 3 , YB 2 or YBO 3 , were found in powders prepared using the other three methods. Bulk material was prepared using direct synthesis from elements by reactive hot-pressing. Influence of temperature and boron content on densification and phase evolution of samples was studied. In situ reaction sintering was performed using conventional hot-pressing at temperatures from 1100°C to 1800°C in vacuum. The amount of boron varied from the stoichiometric content to 5 and 10 wt% excess (with respect to the reaction from elemental powders). Stoichiometric reactions led primarily to the formation of YB 2 and YB 4 and several secondary phases such as Y 2 O 3 , YBO 3 and Y 16.86 B 8 O 38. YB 4 as a main phase was formed only at elevated temperatures (1700°C and 1800°C) but certain content of impurities was still present. Excess of B resulted in the formation of YB 4 as a primary phase in all prepared samples with a small content of YBO 3 and/or Y 16.86 B 8 O 38. Moreover, SEM analysis revealed the presence of unreacted boron.
The Yb–Zn–In system at 400°C: Partial isothermal section with 0–33.3at.% Yb
Journal of Alloys and Compounds, 2009
The phase relations in the ternary system Yb-Zn-In have been established for the partial isothermal section in the 0-33.3 at.% ytterbium concentration range at 400 • C, by researching of more than forty alloys. X-ray powder diffraction (XRPD), optical microscopy (OM) and scanning electron microscopy (SEM), complemented with energy dispersive X-ray spectroscopy (EDS), were used to study the microstructures, identify the phases and characterize their crystal structures and compositions. The phase equilibria of this Yb-Zn-In partial section at 400 • C are characterized by the presence of three extended homogeneity ranges, indium solubility in Yb 13 Zn 58 and YbZn 2 and of zinc solubility in YbIn 2 , and the existence of one ternary intermetallic compound, YbZn 1−x In 1+x , x = ∼0.3. This new compound crystallizes in the UHg 2 structure type (space group P6/mmm), with a = 4.7933(5) Å, c = 3.6954(5) Å. The studied partial isothermal section has eight ternary phase fields at 400 • C.
The crystal structure of Yb2(SO4)3·3H2O and its decomposition product, β-Yb2(SO4)3
Journal of Solid State Chemistry, 2011
Yb 2 (SO 4 ) 3 Á 3H 2 O, synthesised by hydrothermal methods at 220(2) 1C, has been investigated by single crystal X-ray diffraction. Yb 2 (SO 4 ) 3 Á 3H 2 O crystallises in space group Cmc2 1 and is isostructural with Lu 2 (SO 4 ) 3 Á 3H 2 O. The crystal structure has been refined to R 1 ¼ 0.0145 for 3412 reflections [F o 4 3s(F)], and 0.0150 for all 3472 reflections. The structure of Yb 2 (SO 4 ) 3 Á 3H 2 O is a complex framework of YbO 6 octahedra, YbO 8 and YbO 5 (H 2 O) 3 polyhedra and SO 4 tetrahedra. Thermal data shows that Yb 2 (SO 4 ) 3 Á 3H 2 O decomposes between 120 and 190 1C to form b-Yb 2 (SO 4 ) 3 . The structure of a twinned crystal of b-Yb 2 (SO 4 ) 3 was solved and refined using an amplimode refinement in R3c with an R 1 ¼ 0.0755 for 8944 reflections [F o 4 3s(F)], and 0.1483 for all 16,361 reflections. b-Yb 2 (SO 4 ) 3 has a unique structural topology based on a 3D network of pinwheels.
Journal of Alloys and Compounds, 2000
The crystal structure of Y B C was analysed by means of room temperature X-ray single crystal and neutron powder diffractometry. 2 3 2 Y B C crystallises with the Gd B C-type (space group: Cmmm-No. 65, Z52). The unit cell dimensions are: a50.3405(5), 2 3 2 2 3 2 3 23 b51.3765(6), c50.3631(6) nm, b /a54.044, V50.1702 nm the X-ray density is: r 54.57 Mgm. The structure was solved by x combined Patterson-Difference Fourier methods. Residual values are: R 5SuDFu / SuF u50.027, R 50.020, for an asymmetric set of 232 F o w independent reflections (uF u.3s(uF u)). Boron atoms B1, each in triangular metal coordination , form infinite zigzag chains (d 5 o o B1-B1 0.1923 nm) branched with carbon atoms. Bond angles in the chain are w 5124.68. Carbon atoms are at a distance of B1-B1-B1 d 50.1552 in rectangular coordination of four metal atoms. The branched boron chains are connected by a bridging boron atom B2 B1-C linking the carbon atoms in form of a linear bridge at d 50.1442 nm. Rietveld refinement of the neutron powder data from C-B2 11 Y B C (B-isotope) confirms the nuclear structure arrangement as well as the full occupancy of all the non-metal atom sites.