Ag Ga System Research Articles

Probing the Ag – liquid gallium system and its interaction with redox active solutions for catalysis and AgTCNQ formation

The creation of liquid metal alloys that are reacted with species in solution is a relatively new approach to the synthesis of functional nanomaterials. In this work we explore the liquid Ag–Ga system and its interaction with redox active species in aqueous solution in the areas of heterogeneous catalysis and charge transfer complex formation. It was found that when Ag is alloyed with Ga that solid microwires of Ag2Ga were formed over time with a width of ca. 1–1.5 µm of up to 160 µm in length. This Ga/Ag2Ga composite was then investigated for the discolouration of methylene blue dye in both the liquid and solid state where little difference in activity was found resulting in 40% discolouration after 30 min. However, if nitrogen gas was passed through the liquid form of the catalyst the conversion efficiency of the catalyst increased significantly up to 99% after 1 min and could be re-used for up to 10 cycles. In addition, the catalytic conversion of 4-nitrophenol to 4-aminophenol at the liquid Ga/Ag2Ga catalyst was significantly greater than liquid Ga and could be reused for up to 5 cycles. The interaction of liquid Ag–Ga with the well-known electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) was also studied where it was found that a reaction only occurred immediately after mixing Ag microparticles with liquid Ga and before any Ag2Ga microwires were formed. The reaction conditions of bubbling nitrogen gas through the liquid Ag–Ga catalysts in an acetonitrile solution of TCNQ resulted in the time dependent formation of various morphologies of the semi-conducting charge transfer complex AgTCNQ. This work shows that alloying metals with Ga can result in the time dependent formation of a variety of materials under different reaction conditions when exposed to solution based redox active species.

On the 500°C isothermal section of the ternary Eu–Ag–Ga system up to 33.3 at.% Eu

• Isothermal section of the Eu–Ag–Ga (0–33.3 at.% Eu) system at 500 °C. • Identification six new ternary intermetallic phases. • Crystal structure determination of the Eu 2 Ag 13.6–13 Ga 3.3–4 . The isothermal section of the ternary Eu–Ag–Ga system has been studied at 500 °C for the 0–33.3 at.% Eu concentration region. X-ray diffraction techniques, optical microscopy and scanning electron microscopy, complemented with energy dispersive X-ray spectroscopy, were used to identify the phases and characterize their crystal structures and compositions. The crystal structure of selected phases has been refined using powder X-ray diffraction data. This study indicates the formation of six new intermetallic phases in the explored region: EuAg 0.14 Ga 2.86 (own type, related to CeNiSi 2 type), EuAg 2.8 Ga 1.8 (YbAg 2.5 Ga 2.1 type), Eu 4 Ag 14.7 Ga 7.6 (Sc 4 Cu 14.76 Ga 7.51 type), Eu 4 Ag 11.3 Ga 5.7 (own type), Eu 2 Ag 13.6–13 Ga 3.3–4 (Th 2 Zn 17 type) and EuAg 3.2 Ga 0.8 (unknown type).

Thermodynamic description of the binary Ag–Ga system

The AgGaSe 2 as well as AgGaS 2 has been showed to be efficient frequency doubling crystals for infrared radiation such as the 10.6 μm CO 2 laser. The production of these crystals needs good knowledge of the phase relationship. The thermodynamic description of the binary Ag–Ga system has been chosen as a first step for the description of the Ag–Ga–Se and Ag–Ga–S systems. The Calphad approach has been used for this modeling. Good agreement between experimental data and calculated values has been found.

Phase equilibria and crystal structure of the ternary compounds of the La–Ag–Ga system in the region up to 50.0 at.% of La

Phase equilibria and crystal structure of the ternary compounds of the La–Ag–Ga system in the region up to 50.0 at.% of La

Phase Relations of the Ag—Ga—N System.

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The Interactions Between the Components in the Gd—Ag—Ga System.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Phase relations of the Ag–Ga–N system

The phase diagram of the Ag–Ga binary system and the phase relations of the Ag–Ga–N system are studied by DTA and X-ray powder diffraction. The equilibrium phase diagram of the Ag–Ga system is reconstructed. Two intermetallic phases are determined in the Ag–Ga system: the Ag 2Ga compound and a novel δ-Ag 3Ga 2 with the composition about 40 at.% Ga. The novel phase δ-Ag 3Ga 2 which is the product of the peritectic reaction Ag 2Ga + L ↔ δ-Ag 3Ga 2 at 575 K is indexed with an orthorhomic lattice with lattice parameters a = 6.7276(2) Å, b = 3.8840(1) Å, c = 3.2200(1) Å and V = 84.14 Å 3. The temperature-dependent lattice parameters of ζ′-Ag 2Ga with 28 at.% Ga are measured by temperature-dependent X-ray powder diffraction from 93 to 543 K. The linear temperature dependences of the expansion coefficients along the direction of a- and c-axis and volume coefficients are obtained, α a = (1.4741 + 0.0028 T) × 10 −5, α c = (1.1710 + 9.1349 × 10 −4 T) × 10 −5 and α V = (4.1167 + 0.0065 T) × 10 −5, respectively. No ternary phase is found in the Ag–Ga–N system and no solubility of Ag in GaN is observed under the present experimental conditions.

Thermodynamic assessment of the Ag–Ga system

The thermodynamics of the Ag–Ga system are assessed by the CALPHAD approach (calculation of phase diagram). The liquid phase, the solid solution phases of fcc ( α -Ag) and hcp ( ζ ) , the solution compound Ag 2Ga ( ζ ′ ) , the stoichiometric compound Ag 3Ga 2, and the terminal phase of orthorhombic Ga are taken into consideration in this optimization. The liquid phase is described by the association model. The subregular solution model is used for the solid solution phases of fcc and hcp. The solution compound Ag 2Ga is described by the two-sublattice compound energy model (CEM). A set of self-consistent thermodynamic parameters is obtained and the calculated phase diagram and thermodynamic properties are presented and compared with the experimental data from literatures.

The interactions between the components in the Gd–Ag–Ga system

The isothermal section of the Gd–Ag–Ga system at 873 K has been constructed in the region with Gd content less than 50 at.%. The limiting compositions of solid solution regions of the binary compounds and the homogeneity ranges of the ternary ones have been determined. The existence of earlier known ternary gallides Gd 5Ag 1.8Ga 15 (Rb 5Hg 19-type), Gd 3Ag 2.8Ga 8.2 (La 3Al 11-type), GdAg 1.06–1.34Ga 1.94–1.66 (β-YbAgGa 2-type), GdAg 0.35Ga 1.65 (CeCd 2-type), GdAg 0.7-0.4Ga 1.3–1.6 (CaIn 2-type), GdAg 1.00–0.75Ga 1.00–1.25 (KHg 2-type) has been confirmed. The crystal structure of the Gd 3Ag 2.8Ga 8.2 compound (La 3Al 11-type) was refined for the first time ( R I/ R P = 0.065/0.118).

Structures of ζ and ζ′ Phases in the Ag—Ga System.

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Structures of the ζ and ζ′ phases in the Ag–Ga system

The crystal structures of the ζ-phase and ζ′-phase have been determined by X-ray powder diffraction and refined by Rietveld method. The space group of the ζ′-phase is P 6 ¯ 2 m with the lattice parameters a = 7.7710(1) and c = 2.8788(1) Å. The ideal formula is Ag 2Ga (real composition Ag 2+ x Ga 1− x , x = 0.16) and the chemical formula per unit cell is Z = 3. Six Ag atoms occupy the 3g positions with x = 0.63970(8) and the 3f positions with x = 0.30347(9), respectively. Three Ga atoms occupy the 2c and the 1b sites. The ζ-phase is obtained by quenching the sample containing 20 at.% Ga from 500 °C to room temperature. Its space group is close-packed hexagonal, P6 3/ mmc, and the lattice parameters are a = 2.8818(1) and c = 4.6956(1) Å. There are 2 atoms (1.5Ag + 0.5Ga) per unit cell, which occupy the 2c site statistically. The relation between the structures of the ζ- and ζ′-phase is discussed.

The Gallium‐Rich Region of the Ce—Ag—Ga System.

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The gallium-rich region of the Ce–Ag–Ga system

The interaction between the components in the Ga-rich region of the Ce–Ag–Ga system has been studied at 523, 573 and 873 K. The existence of the earlier known gallides CeGa 6 (PuGa 6-type) at 523 and 573 K and CeAg 0.68Ga 3.32 (BaAl 4-type) in the whole temperature interval has been confirmed. The compound CeAg 1.25Ga 4.25, existing at 523 K, has been found to crystallize in its own type of structure: space group P4/mcc, a = 4.2723(1) Å, c = 15.3468(3) Å, R I = 0.089; and the compound CeAg 4.12Ga 6.88 (BaHg 11-type, space group Pm3m, a = 8.7159(1) Å, R I = 0.081), existing at 573 K has been discovered for the first time.

The Y–Ag–Ga system

The isothermal section at 670 K of the Y–Ag–Ga system in the region of 0–33 at.% Y has been constructed using X-ray diffraction data. The existence of earlier known ternary gallides has been confirmed. Their homogeneity regions, atomic coordinates and distribution of atoms in the structures have been determined: Y 3Ag 2.55Ga 8.45 (La 3Al 11-type structure, a = 0.4310(1) nm, b = 1.2865(3) nm, c = 0.9552(3) nm, R F = 0.043), YAg 0.22Ga 1.78 (CaIn 2-type structure, a = 0.44565(1) nm, c = 0.72032(2) nm, R I = 0.081), YAg 0.74Ga 1.26 (KHg 2-type structure, a = 0.45302(2) nm, b = 0.70805(3) nm, c = 0.78056(3) nm, R I = 0.059). The crystal structure of the new ternary compound YAg 1.1Ga 1.9 (β-YbAgGa 2-type structure, Pnma, a = 0.69654(3) nm, b = 0.43391(2) nm, c = 1.02126(5) nm, R I = 0.087) has been studied for the first time.

The Tb—Ag—Ga System.

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The Tb–Ag–Ga system

The isothermal section of the Tb–Ag–Ga system at 873 K has been constructed in the region up to 70 at.% Ga. The interaction between components in the region with higher gallium content has been studied at 573 K. The composition limits of the solid solution ranges of the binary compounds and the homogeneity ranges of the ternary ones have been determined. The existence of earlier known ternary gallides Tb 3Ag 2.8Ga 8.2 (La 3Al 11-type), TbAg 0.4–0.7Ga 1.6–1.3 (CaIn 2-type), TbAg 0.9–1.2Ga 1.1–0.8 (KHg 2-type) has been confirmed. The compounds TbAg 0.5Ga 3.5 (unknown structure), Tb 4Ag 0.9Ga 12.1 (Y 4PdGa 12-type, space group Im 3m , α=0.86537(2) nm, R Brag=0.039), and TbAg 1.2Ga 1.8 (β-YbAgGa 2-type, space group Pnma, a=0.69742(3), b=0.43587(1), c=1.02098(7) nm, R I=0.070) have been found for the first time.

Phase relations and crystal structures in the Ag–Ga system

Abstract The Ag–Ga phase diagram and the ζ-Ag2Ga↔ζ′-Ag2Ga transformation have been investigated by use of optical, scanning and transmission electron microscopy combined with X-ray powder diffraction and thermal differential analysis. On the basis of the present study a new equilibrium phase diagram for the Ag–Ga system is proposed. Only two intermetallic phases are found in the Ag–Ga system: ζ′ and ζ. The compositional change of Ga in ζ′ is described by replacing Ga atoms in 1b position in space group P 6 2m with Ag atoms. In alloys having 25–40 wt.% Ga, the high temperature ζ-Ag2Ga is found to decompose into a Ga-rich liquid and solid ζ′-Ag2Ga at 302°C. In Ga-poor alloys (15 wt.%), the high temperature ζ-Ag2Ga is found to decompose into α-Ag and liquid at 611°C and into α-Ag and ζ′-Ag2Ga at 395°C.

Magnetic and Thermodynamical Properties of Liquid Ag-Polyvalent Alloys

The magnetic susceptibilities of liquid Ag–In, Ag–Sn, Ag–Ga and Ag–Zn alloy systems have been measured over a wide temperature range from 600 to 1085° C. The magnetic susceptibility curves at 1010° C were plotted against the alloy composition, which are different from one another. The temperature coefficients of their magnetic susceptibilities against the composition were very similar, showing a sharp minimum at about 90 at%Ag and a broad maximum at about 70 at%Ag, except for those of the Ag–Zn system. The curve of the concentration-concentration fluctuation in the long wavelength limit S CC (0) of those alloys has been estimated by using the experimental EMF data compiled in the literatures. Two pronounced minima exist in the S CC (0) curves at about 35 and 70 at%Ag, except for the Ag–Ga system.

Room temperature interactions in Ag-metals thin film couples

The results of room temperature interactions of silver and various metals in thin films are presented. It has been found that aluminium, gold, bismuth, chromium, copper, antimony and samarium do not react with silver under the conditions given, but cadmium, gallium, indium, tin, tellurium and zinc do, and the reactions lead to the formation of corresponding intermetallic compounds. In the AgGa system only one compound is formed, which has been identified as Ag 3Ga. In the AgIn system, with less than 50 wt.% In, one compound is formed and this has been identified as Ag 2In. A compound formed with over 50 wt.% In has been identified as AgIn 2 LT (low temperature phase). Between 60 and 120°C this compound transforms into AgIn 2 MT (medium temperature phase). In the AgSn system the compound Ag 3Sn is formed and in the AgTe system the compounds Ag 2Te and Ag 5Te 3 are formed.

On the β phase of the gold-gallium system

An X-ray diffraction and metallographic investigation of the β phase of the gold-gallium system has been carried out. The X-ray powder pattern of the β phase closely resembles the pattern of the trigonal ζ′ phase of the AgGa system, but back reflection Laue patterns show that the β phase has true hexagonal symmetry. Metallographic evidence suggests the presence of a massive transformation similar to that found in CuGa alloys.