Eutectic Flux Research Articles

Low-temperature sintering of Ba(Zr,Y)O3-based proton conducting oxides using BaO–CuO eutectic flux as sintering aid

The major barrier to the practical application of Ba(Zr,Y)O3 (BZY) as an electrolyte material for proton-conducting fuel cells (PCFCs) lies in its extremely inferior sintering characteristics. In this research, flux composed of 28mol% BaO and 72mol% CuO was employed as a novel sintering aid for BZY. Incorporation of nano-crystalline BaO–CuO flux, with a eutectic point of 890°C, remarkably enhanced the sintering behavior of BZY due to the formation of a transient liquid phase, and a relative density of up to 97% of the theoretical density was obtained at 1300°C with a short soaking time of 2h.

Influence of rare earth cation size on the crystal structure in rare earth silicates, Na2RESiO4(OH) (RE = Sc, Yb) and NaRESiO4 (RE = La, Yb)

Crystals of Na2ScSiO4(OH) and Na2YbSiO4(OH) were synthesized at low temperatures using a sodium hydroxide based hydroflux, while crystals of NaLaSiO4 and NaYbSiO4 were grown at high temperatures using a sodium fluoride/sodium chloride eutectic flux. Both structure types were crystallized under reaction conditions that, when used for medium sized rare earths (RE = Pr, Nd, Sm – Tm) yield the Na5RE4X[SiO4]4 structure type, where X is OH in the hydroflux conditions and F in the eutectic flux conditions. Herein, we report the synthesis, structure, size effect, and magnetic properties of these compositions and introduce the new structure type of Na2RESiO4(OH), which crystallizes in the orthorhombic space group Pca21, of NaLaSiO4, which crystallizes in the orthorhombic space group Pna21, and of NaYbSiO4, which crystallizes in the orthorhombic space group Pnma, where both NaRESiO4 compounds have one silicon structural analog.

ChemInform Abstract: Single Crystal Growth and Characterization of the First Reduced Lanthanum Molybdenum Oxychloride, La20Mo12O63Cl4, with an Unusual Trigonal Prismatic MoO6 Unit.

AbstractDeep blue single crystals of the title compound are synthesized from mixtures of La2O3, MoO3, and Mo powder in CsCl/LiCl eutectic flux (silica tube, 800 °C, 24 h, 80% yield).

ChemInform Abstract: Single Crystal Growth and Characterization of the Reduced Barium Sodium Siliconiobate, Ba3Na0.32Nb6O12 (Si2O7)2.

AbstractSingle crystals of the title compound are prepared from NaNbO3 in a BaCl2/NaCl eutectic flux in the presence of Zn (evacuated silica tube (wall reaction), 1050 °C, 48 h, ≈75% yield).

ChemInform Abstract: Crystal Growth, Structures, and Properties of the Complex Borides, LaOs2Al2B and La2Os2AlB2.

AbstractSingle crystals of the new compounds LaOs2Al2B (I) and La2Os2AlB2 (II) are grown from stoichiometric amounts of the elements in a La/Ni eutectic flux (alumina crucible covered with quartz wool in evacuated silica tubes, 1000 °C, 12 h; cooling from 850 to 650 °C within 84 h).

The low temperature electrochemical growth of iron, nickel and other metallic single crystals from halide eutectic fluxes in a temperature gradient

Single crystals of metallic Fe, Ni, Co, Cr, Al, Cu, Ag, Au, Pd, Pt and a few alloys were grown using the AlCl3/KCl and CsCl/NaCl/KCl fluxes for Men+ transport and an inert metallic wire for electron transport in a permanent temperature gradient from 350–600°C that produced single crystalline samples with dimensions of approximately 2×2×2mm3. Energy dispersive X-ray spectroscopy established crystal formation of pure metals.

Nd8Co4−xAlxGe2C3: A case study in flux growth of lanthanide-rich intermetallics

The intermetallic Nd8Co4−xAlxGe2C3 (x≈0.65) was prepared from reaction of germanium and carbon in Nd/Co eutectic flux in an alumina crucible. This phase exhibits a new structure type in orthorhombic space group Pbcm, with unit cell parameters a=8.001(1)Å, b=11.696(2)Å, c=15.020(3)Å (Z=4; R1=0.0234). The structure features germanium-centered neodymium clusters Ge@Nd9 which share faces to form layers separated by zigzag chains of cobalt atoms capped by carbon. Density of states calculations confirm that this compound is metallic, and indicate that the cobalt should not have a magnetic moment. This is supported by magnetic susceptibility measurements which show a low temperature ferromagnetic ordering at TC=50K due to the Nd3+ ions. Magnetization field dependence studies on single crystals indicate this compound is a strong ferromagnet with large anisotropy; the Nd3+ magnetic moments align along the a-axis.

Crystal Growth, Structures, and Properties of the Complex Borides, LaOs2Al2B and La2Os2AlB2.

Single crystals of two novel quaternary metal borides, LaOs2Al2B and La2Os2AlB2, have been grown from La/Ni eutectic fluxes. LaOs2Al2B crystallizes in tetragonal space group P4/mmm with the CeCr2Si2C-type structure, and lattice parameters a = 4.2075(6) Å and c = 5.634(1) Å. La2Os2AlB2 exhibits a new crystal structure in monoclinic space group C2/c with lattice parameters a = 16.629(3) Å, b = 6.048(1) Å, c = 10.393(2) Å, and β = 113.96(3)°. Both structures are three-dimensional frameworks with unusual coordination (for solid-state compounds) of the boron atoms by transition metal atoms. The boron atom is square planar in LaOs2Al2B, whereas it exhibits linear and T-shaped geometries in La2Os2AlB2. Electrical resistivity measurements reveal poor metal behavior (ρ300K ∼ 900 μΩ cm) for La2Os2AlB2, consistent with the electronic band structure calculations, which also predict a metallic character for LaOs2Al2B.

Single crystal growth and characterization of the first reduced lanthanum molybdenum oxychloride, La20Mo12O63Cl4, with an unusual trigonal prismatic MoO6 unit

The use of a KCl/CsCl alkali eutectic flux under reducing conditions facilitated the crystal growth of the mixed valent Mo(V)/Mo(VI) compound La20Mo12O63Cl4. La20Mo12O63Cl4 crystallizes in the noncentrosymmetric hexagonal space group P-62m with a = 10.2241(2) Å and c = 15.0768(4) Å, which represents a new structure type exhibiting a three-dimensional crystal structure containing three different molybdenum coordination environments, MoO5 square pyramids, MoO6 trigonal prisms, and MoO5 trigonal bipyramids. The temperature dependence of the magnetic susceptibility was measured and La20Mo12O63Cl4 was found to be paramagnetic across the entire 2–300 K temperature range measured. Although noncentrosymmetric, La20Mo12O63Cl4 was not found to be second harmonic generation active. La20Mo12O63Cl4 was further characterized by UV/Vis spectroscopy.

Single crystal growth and characterization of the reduced barium sodium siliconiobate, Ba3Na0.32Nb6O12(Si2O7)2

Single crystals of Ba3Na0.32Nb6O12(Si2O7)2 were grown for the first time. The use of an alkali/alkaline earth eutectic flux facilitated the crystal growth. Ba3Na0.32Nb6O12(Si2O7)2, a mixed valent Nb(V)/Nb(IV) compound, crystallizes in the noncentrosymmetric hexagonal space group P-62m with a = 8.9998(10) Å and c = 7.8119(17) Å. The temperature dependence of the magnetic susceptibility was measured and found to be paramagnetic across the entire 2–300 K temperature range measured. Although noncentrosymmetric, Ba3Na0.32Nb6O12(Si2O7)2 was not found to be second harmonic generation active. Ba3Na0.32Nb6O12(Si2O7)2 was further characterized by IR and UV/Vis spectroscopies.

Fabrication of c-axis Oriented Epitaxial EuBa2Cu3O7-δ and EuBa2Cu4O8 Films on SrTiO3 (100) Substrate by Molten Hydroxide Method at 450°C

EuBa2Cu3O7-δ (Eu123) and EuBa2Cu4O8 (Eu124) films oriented in c-axis were deposited on SrTiO3 (100) substrates with eutectic NaOH-KOH flux at 450°C. Synthesized phase has changed by using various types of barium source materials. Pure Eu124 films showed superconducting transition at ∼70K, zero-resistance was not observed for Eu123/124 two-phase films. One of the possible reasons of this is Eu/Ba substitution of Eu123 phase. According to Tc of the Eu124, the molten hydroxide method enables to deposit high-quality Eu124 films.

ChemInform Abstract: Synthesis, Crystal Structure, and Magnetic Properties of Novel Intermetallic Compounds R2Co2SiC (R: Pr, Nd).

AbstractThe title compounds are prepared by reaction of silicon and carbon in either a Pr/Co or a Nd/Co eutectic flux (alumina crucible, 950 °C, 12 h and 850 °C for 48 h).

Crystal growth and structure of three new neodymium containing silicates: Na0.50Nd4.50(SiO4)3O, Na0.63Nd4.37(SiO4)3O0.74F0.26 and Na4.74Nd4.26(O0.52F0.48)[SiO4

Single crystals of Na0.50Nd4.50(SiO4)3O, Na0.63Nd4.37(SiO4)3O0.74F0.26, and Na4.74Nd4.26(O0.52F0.48)[SiO4]4 were synthesized via flux growth using a NaF/KF eutectic flux and the crystal structure was determined by single crystal X-ray diffraction. Na0.50Nd4.50(SiO4)3O and Na0.63Nd4.37(SiO4)3O0.74F0.26 adopt the apatite structure and crystallize in the hexagonal space group P63/m, while Na4.74Nd4.26(O0.52F0.48)[SiO4]4 crystallizes in the tetragonal space group I-4 and exhibits rare-earth mixing on the sodium site. The unit cells of the crystals are a = 9.5400(3) Å and c = 7.0331(5) Å for Na0.50Nd4.50(SiO4)3O, a = 9.5533(3) Å and c = 7.0510(4) Å for Na0.63Nd4.37(SiO4)3O0.74F0.26, and a = 12.1255(3) Å and c = 5.4656(2) Å for Na4.74Nd4.26(O0.52F0.48)[SiO4]4. These three compounds exhibit three-dimensional crystal structures that are discussed in detail in this paper.

Synthesis, crystal structure, and magnetic properties of novel intermetallic compounds R2Co2SiC (R = Pr, Nd).

The intermetallic compounds R2Co2SiC (R = Pr, Nd) were prepared from the reaction of silicon and carbon in either Pr/Co or Nd/Co eutectic flux. These phases crystallize with a new stuffed variant of the W2CoB2 structure type in orthorhombic space group Immm with unit cell parameters a = 3.978(4) Å, b = 6.094(5) Å, c = 8.903(8) Å (Z = 2; R1 = 0.0302) for Nd2Co2SiC. Silicon, cobalt, and carbon atoms form two-dimensional flat sheets, which are separated by puckered layers of rare-earth cations. Magnetic susceptibility measurements indicate that the rare earth cations in both analogues order ferromagnetically at low temperature (TC ≈ 12 K for Nd2Co2SiC and TC ≈ 20 K for Pr2Co2SiC). Single-crystal neutron diffraction data for Nd2Co2SiC indicate that Nd moments initially align ferromagnetically along the c axis around ∼12 K, but below 11 K, they tilt slightly away from the c axis, in the ac plane. Electronic structure calculations confirm the lack of spin polarization for Co 3d moments.

Mechanisms for microstructure enhancement in flux-assisted growth of barium titanate on sapphire

Abstract

An Environmentally Friendly Process Involving Refining and Membrane-Based Electrolysis for Magnesium Recovery from Partially Oxidized Scrap Alloy

Magnesium is recovered from partially oxidized scrap alloy by combining refining and solid oxide membrane (SOM) electrolysis. In this combined process, a molten salt eutectic flux (45 wt.% MgF2–55 wt.% CaF2) containing 10 wt.% MgO and 2 wt.% YF3 was used as the medium for magnesium recovery. During refining, magnesium and its oxide are dissolved from the scrap into the molten flux. Forming gas is bubbled through the flux and the dissolved magnesium is removed via the gas phase and condensed in a separate condenser at a lower temperature. The molten flux has a finite solubility for magnesium and acts as a selective medium for magnesium dissolution, but not aluminum or iron, and therefore the magnesium recovered has high purity. After refining, SOM electrolysis is performed in the same reactor to enable electrolysis of the dissolved magnesium oxide in the molten flux producing magnesium at the cathode and oxygen at the SOM anode. During SOM electrolysis, it is necessary to decrease the concentration of the dissolved magnesium in the flux to improve the faradaic current efficiency and prevent degradation of the SOM. Thus, for both refining and SOM electrolysis, it is very important to measure and control the magnesium solubility in the molten flux. High magnesium solubility facilitates refining whereas lower solubility benefits the SOM electrolysis process. Computational fluid dynamics modeling was employed to simulate the flow behavior of the flux stirred by the forming gas. Based on the modeling results, an optimized design of the stirring tubes and its placement in the flux are determined for efficiently removing the dissolved magnesium and also increasing the efficiency of the SOM electrolysis process.

Synthesis of by the Flux Method

has been successfully synthesized using Bi2O3–B2O3 eutectic flux. In particular, we succeeded in synthesizing a low-temperature-phase crystal (α-) at 1073 K as well as high-temperature-phase crystal (β-). The morphology of α- and β- particles prepared by the flux method is a euhedral crystal. In contrast, the morphology of particles prepared by solid state reaction differs: α- is aggregated and β- is necked. Ultraviolet-visible diffuse reflectance spectra indicate that the absorption edge is at a longer wavelength for β- than for α- with β- absorbing light of wavelengths up to nearly 400 nm.

A Tale of Two Metals: New Cerium Iron Borocarbide Intermetallics Grown from Rare-Earth/Transition Metal Eutectic Fluxes

R(33)Fe(14-x)Al(x+y)B(25-y)C(34) (R = La or Ce; x ≤ 0.9; y ≤ 0.2) and R(33)Fe(13-x)Al(x)B(18)C(34) (R = Ce or Pr; x < 0.1) were synthesized from reactions of iron with boron, carbon, and aluminum in R-T eutectic fluxes (T = Fe, Co, or Ni). These phases crystallize in the cubic space group Im3m (a = 14.617(1) Å, Z = 2, R(1) = 0.0155 for Ce(33)Fe(13.1)Al(1.1)B(24.8)C(34), and a = 14.246(8) Å, Z = 2, R(1) = 0.0142 for Ce(33)Fe(13)B(18)C(34)). Their structures can be described as body-centered cubic arrays of large Fe(13) or Fe(14) clusters which are capped by borocarbide chains and surrounded by rare earth cations. The magnetic behavior of the cerium-containing analogs is complicated by the possibility of two valence states for cerium and possible presence of magnetic moments on the iron sites. Temperature-dependent magnetic susceptibility measurements and Mössbauer data show that the boron-centered Fe(14) clusters in Ce(33)Fe(14-x)Al(x+y)B(25-y)C(34) are not magnetic. X-ray photoelectron spectroscopy data indicate that the cerium is trivalent at room temperature, but the temperature dependence of the resistivity and the magnetic susceptibility data suggest Ce(3+/4+) valence fluctuation beginning at 120 K. Bond length analysis and XPS studies of Ce(33)Fe(13)B(18)C(34) indicate the cerium in this phase is tetravalent, and the observed magnetic ordering at T(C) = 180 K is due to magnetic moments on the Fe(13) clusters.

An Experimental Study of a Flux Modulated Solid State Metathesis Reaction

AbstractA solid state metathesis (SSM) reaction was investigated with respect to the formation of rare‐earth carbodiimides, the role of the co‐produced salt (LiCl), and the eutectic flux medium (LiCl/KCl). A SSM reaction is characterized by an exothermic reaction in which a salt (often LiCl) is coproduced. When the salt melts, it can serve as a useful medium for the crystallization of a desired product. An improved crystal growth can be observed by using an eutectic flux. However, the composition of an eutectic LiCl/KCl flux is altered when LiCl is produced during the reaction. The thermal effects concerning the endothermic melting of the flux and the exothermic ingnition of the SSM reaction may compensate each other, which is not necessarily a drawback for the reaction to proceed.

Flux growth of a new cobalt–zinc–tin ternary phase Co 7+ xZn 3− xSn 8 and its relationship to CoSn

The intermetallic compound Co 7+ x Zn 3− x Sn 8 (−0.2< x<0.2) forms from the reaction of cobalt in zinc/tin eutectic flux. This phase has a new structure type in orthorhombic space group Cmcm, with unit cell parameters a=4.138(1) Å, b=12.593(4) Å, and c=11.639(4) Å ( Z=2; R 1=0.0301). Varying the amount of cobalt in the synthesis leads to formation of a superstructure in space group Pnma, with lattice parameters a=12.5908(2) Å, b=11.6298(3) Å, and c=8.2704(2) Å ( Z=4; R 1=0.0347). A Co/Zn mixed site and a partially occupied Co site in the Cmcm structure order to form the Pnma supercell. TGA/DSC studies indicate that the binary phase CoSn initially forms in the flux at 1173 K, and then reacts with the zinc in the cooling solution to form the ternary structure at 823 K. This phase exhibits Pauli paramagnetic behavior.