Binary Precursors Research Articles

Theoretical prediction of structural parameters, band-gap energies, and mixing enthalpies of Sc1−x In x As alloys

Structural parameters, band-gap energies, and mixing enthalpies of Sc1−xInxAs alloys were calculated using the full-potential linearized–augmented plane wave method. These calculations are based on density functional theory, within local density approximation, and generalized gradient approximation for the exchange and correlation potential. Given that the binary precursor compounds ScAs and InAs crystallize in rock-salt and zinc-blende, respectively, we made calculations for the ternary alloys in these two phases. The effect of composition x on structural parameters, band-gap energies, and mixing enthalpies was analyzed for x = 0, 0.25, 0.5, 0.75, 1. The effect of atomic composition on lattice constant, bulk modulus, and band-gap energy shows nonlinear dependence on concentration x. Deviations of the lattice constant from Vegard’s law and deviations of the bulk modulus and gap-energy from linear concentration dependence were found. We have found a metallic character for rock-salt Sc1−xInxAs alloys, while the zinc-blende Sc1−xInxAs alloys are semiconductors. Our results show that the band-gap undergoes a direct (\(X \rightarrow X\))-to-direct (\(\Upgamma\rightarrow \Upgamma\)) transition at a given indium composition. The physical origin of the band-gap bowing in zinc-blende Sc1−xInxAs alloys was investigated. To study the thermodynamic stability of Sc1−xInxAs alloys, a regular-solution model was used. This resulted in lower mixing enthalpies for zinc-blende Sc1−xInxAs alloys.

Non-injection synthesis of Cu2ZnSnS4nanocrystals using a binary precursor and ligand approach

We present a non-injection, one-pot synthesis of kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) that allows for multi-gram yields with precise control of the NCs' metal composition. This is enabled through the selective use of a binary sulfur precursor and ligand reaction mixture, which acts to decouple the nucleation and growth stages.

Air-stable solution processed Cu2ZnSn(Sx,Se(1-x))4 thin film solar cells: influence of ink precursors and preparation process

ABSTRACTQuaternary semiconductors, Cu2ZnSnS4 and Cu2ZnSnSe4 which contain only earth-abundant elements, have been considered as the alternative absorber layers to Cu(In,Ga)Se2 (CIGS) for thin film solar cells although CIGS-based solar cells have achieved efficiencies over 20 %. In this work we report an air-stable route for preparation of Cu2ZnSn(Sx,Se(1-x))4 (CZTSSe) thin film absorbers by a solution process based on the binary and ternary chalcogenide nanoparticle precursors dispersed in organic solvents. The CZTSSe absorber layers were achieved by spin coating of the ink precursors followed by annealing under Ar/Se atmosphere at temperature up to 580°C. We have investigated the influence of the annealing temperature on the reduction or elimination of detrimental secondary phases. X-ray diffraction combined with Raman spectroscopy was utilized to better identify the secondary phases existing in the absorber layers. Solar cells were completed by chemical bath deposited CdS buffer layer followed by sputtered i-ZnO/ZnO: Al bi-layers and evaporated Ni/Al grids.

Fabrication of CuInSe2 light absorption materials from binary precursors via wet chemical process

CuInSe2 materials with a chalcopyrite structure were successfully synthesized from binary precursors through the reaction paths: (A) Cu2Se+In2Se3→2CuInSe2, (B) CuSe+InSe→CuInSe2, (C) Cu2Se+2InSe+Se→2CuInSe2 via a wet-chemical process. The binary precursors such as CuSe, Cu2Se, InSe and In2Se3 can be synthesized in a facile chemical route from suitable resources at different stoichiometric ratios. The phase analysis, purity, morphology, and thermal stability of the products have been studied by XRD, SEM, EDS, and TGA. The CuInSe2 produced by this method possess a band gap of 1.05eV calculated from the UV–vis spectrum.

Ternary PtMnX/C (X=Fe, Co, Ni, Cu, Mo and, Sn) Alloy Catalysts for Ethanol Electrooxidation

In this study, ternary PtMnX/C (X=Fe, Co, Ni, Cu, Mo and, Sn) alloys catalysts have been synthesized and characterized by ICP, XRD, TEM and cyclic voltammetry. XRD studies showed that PtMnX/C (X=Fe, Co, Ni, Cu and Mo) alloys have been formed without significant free Mn and X co-catalysts. For PtMnSn/C, in addition to alloy formation, significant free Sn-oxides are present. Cyclic voltammetry and chronoamperometry of the ternary alloys reveled that except PtMnSn/C which illustrate moderate activity, all the catalysts PtMnX/C (X=Fe, Co, Ni, Cu and, Mo) showed superior electrocatalytic activity toward ethanol electrooxidation compared to the binary alloy PtMn/C precursor. Furthermore, shifts of the onset potentials of ethanol oxidation toward less positive values were also recorded demonstrating a facilitated oxidation with the ternary alloys compared to PtMn/C binary alloy precursor.

Nonequilibrium structure of Zn2SnO4 spinel nanoparticles

Zinc stannate (Zn2SnO4) nanoparticles with an average size of about 26 nm are synthesized via single-step mechanochemical processing of binary oxide precursors (ZnO and SnO2) at ambient temperature, without the need for the subsequent calcination, thus making the synthesis route very simple and cost-effective. The mechanically induced phase evolution of the 2ZnO + SnO2 mixture is followed by XRD and by a variety of spectroscopic techniques including 119Sn MAS NMR, Raman spectroscopy, 119Sn Mossbauer spectroscopy, and XPS. High-resolution TEM studies reveal a non-uniform structure of mechanosynthesized Zn2SnO4 nanoparticles consisting of a crystalline core surrounded by a structurally disordered surface shell. Due to the ability of the applied solid-state spectroscopies to probe the local environment of Sn cations, valuable complementary insight into the nature of the local structural disorder of mechanosynthesized Zn2SnO4 is obtained. The findings hint at a highly nonequilibrium state of the as-prepared stannate characterized by its partly inverse spinel structure and the presence of deformed polyhedra in the surface shell of nanoparticles.

Making practical use of the pseudo-element concept: an efficient way to ternary intermetalloid clusters by an isoelectronic Pb−–Bi combination

Syntheses of [K([2.2.2]crypt)](+) salts of binary Pb-Bi Zintl anions and their reaction with ZnPh(2) or Ni(cod)(2), yielding ternary intermetalloid Ni-Pb-Bi or Zn-Pb-Bi clusters, proved the use of binary precursors with fully isoelectronic atoms as an efficient and thus valuable synthetic approach to this class of clusters. (207)Pb NMR and ESI mass spectra provided insight into the solution behavior of the binary or ternary cages.

Size-Dependent Morphology of Dealloyed Bimetallic Catalysts: Linking the Nano to the Macro Scale

Chemical dealloying of Pt binary alloy precursors has emerged as a novel and important preparation process for highly active fuel cell catalysts. Dealloying is a selective (electro)chemical leaching of a less noble metal M from a M rich Pt alloy precursor material and has been a familiar subject of macroscale corrosion technology for decades. The atomic processes occurring during the dealloying of nanoscale materials, however, are virtually unexplored and hence poorly understood. Here, we have investigated how the morphology and intraparticle composition depend on the particle size of dealloyed Pt-Co and Pt-Cu alloy nanoparticle precursor catalysts. To examine the size-morphology-composition relation, we used a combination of high-resolutionscanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), electron energy loss (EEL) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), and surface-sensitive cycling voltammetry. Our results indicate the existence of three distinctly different size-dependent morphology regimes in dealloyed Pt-Co and Pt-Cu particle ensembles: (i) The arrangement of Pt shell surrounding a single alloy core ("single core-shell nanoparticles") is exclusively formed by dealloying of particles below a characteristic diameter d(multiple cores) of 10-15 nm. (ii) Above d(multiple cores), nonporous bimetallic core-shell particles dominate and show structures with irregular shaped multiple Co/Cu rich cores ("multiple cores-shell nanoparticles"). (iii) Above the second characteristic diameter d(pores) of about 30 nm, the dealloyed Pt-Co and Pt-Cu particles start to show surface pits and nanoscale pores next to multiple Co/Cu rich cores. This structure prevails up to macroscopic bulklike dealloyed particles with diameter of more than 100 nm. The size-morphology-composition relationships link the nano to the macro scale and provide an insight into the existing material gap of dealloyed nanoparticles and highly porous bulklike bimetallic particles in corrosion science.

Disubstituted dialkoxysilane precursors in binary and ternary sol–gel systems for lipase immobilization

The disubstituted dimethyldiethoxysilane (DMDEOS), methyl(phenyl)diethoxysilane (MPDEOS) and diphenyldiethoxysilane (DPDEOS) were used in binary silane precursor systems in combination with tetraethoxysilane (TEOS) for the immobilization of lipase from Pseudomonas fluorescens (Lipase AK). In addition, ternary silane precursor systems with TEOS and octyltriethoxysilane (OTEOS) or phenyltriethoxysilane (PTEOS) were also studied for encapsulation. The best performing ternary sol–gel preparations (418–736% activity yields of the immobilized enzyme with 1-phenylethanol rac-1a as compared to the native form) were tested as biocatalysts for kinetic resolutions of rac-1a, 1-phenylpropan-2-ol rac-1b and 4-phenylbutan-2-ol rac-1c. Because the catalytic properties and the operational stability of the DMDEOS-containing preparations proved to be superior to all the tested free and sol–gel entrapped Lipase AK biocatalysts in batch mode, the kinetic resolutions of rac-1a and rac-1b were performed with the TEOS/PTEOS/DMDEOS 4:1:1 Lipase AK in a continuous-flow reactor as well.

Study of Cu 2ZnSnSe 4 monograin formation in molten KI starting from binary chalcogenides

The present study deals with the possible chemical interactions of CuSe, SnSe, and ZnSe in molten KI as a flux material in vacuum ampoules. The aim is to find suitable preparation conditions for the synthesis of Cu 2ZnSnSe 4 monograin powders as an absorber material for solar cells. Impurities in the precursor materials and in the product powders were determined by inductively coupled plasma mass spectrometry. Differential thermal analysis was used to determine thermal effects. Phase composition in the mixtures of binary precursors and KI was determined by X-ray diffraction and Raman spectroscopy. It was found that no new compound was formed in the CuSe/KI, ZnSe/KI and SnSe/KI mixtures. The solubility of the binary chalcogenides in KI at 740 °C was determined.

Role of Na in reaction pathways and kinetics of CuInSe 2 formation from stacked binary precursors

Binary stacked In 2Se 3/CuSe precursors were prepared onto substrates with different types of sodium (Na) sources, i.e., soda-lime glass (SLG), sodium-free glass (SFG), SFG with Na-doped Mo layers (Mo:Na), in a co-evaporation system. SIMS depth profiles for In 2Se 3 precursors deposited at 400 °C demonstrated that the different amounts of Na diffused out of each Na source. High-temperature XRD experiments revealed that there was no significant effect of Na on the reaction path of CuInSe 2 formation from In 2Se 3/CuSe stacked precursor. The reaction rate of the precursor without Na (i.e., SFG/Mo/In 2Se 3/CuSe) was found to be higher than that of those with Na (i.e., SLG/Mo/In 2Se 3/CuSe and SFG/Mo:Na(750 nm)/Mo/In 2Se 3/CuSe).

Neither Electron‐Precise nor in Accordance with Wade–Mingos Rules: The Ternary Cluster Anion [Ni2Sn7Bi5]3−

The birdcage: The title anion, which contains two endohedral d10 metal atoms, is the second known ternary cluster anion comprising only metal atoms (see picture: Sn orange, Sn/Bi blue, Ni black). The K([2.2.2]crypt) salt was obtained upon reaction of the binary precursor [Sn2Bi2]2− with [Ni(cod)2] in ethylenediamine/toluene by a complicated fragmentation/re-arrangement process. X-ray diffraction and DFT calculations confirm the composition of the anion.

Controlled Aqueous Solution Synthesis of Platinum–Palladium Alloy Nanodendrites with Various Compositions Using Amphiphilic Triblock Copolymers

In a recent study, we demonstrated that Pluronic F127 triblock copolymer plays a critical role in the formation of dendritic Pt nanostructures (L. Wang, Y. Yamauchi, J. Am. Chem. Soc. 2009, 131, 9152-9153). Herein, we expand this concept to produce novel dendritic Pt-Pd alloy nanoparticles. In this paper, a very simple, one-step and efficient route is proposed to directly produce dendritic Pt-Pd alloy nanoparticles with high surface area in high yield, which is carried out simply by stirring an aqueous solution that contains K(2)PtCl(4) and Na(2)PdCl(4) binary precursors in the presence of Pluronic F127 block copolymer and ascorbic acid at room temperature within 30 min without the need for any template, seed-mediated growth, or additive. By simply changing the compositional ratios of the Pt and Pd sources in the precursor solutions, Pt-Pd nanodendrites with various compositions can be easily produced. Because of its unique simplicity, the proposed approach can be considered as a powerful strategy for producing Pt-Pd alloy nanoparticles with unique nanoarchitectures for commercial devices.

Dealloyed binary PtM 3 (M = Cu, Co, Ni) and ternary PtNi 3M (M = Cu, Co, Fe, Cr) electrocatalysts for the oxygen reduction reaction: Performance in polymer electrolyte membrane fuel cells

Dealloyed Pt bimetallic nanoparticles are highly active electrocatalysts for the electroreduction of molecular oxygen (ORR), the key barrier to more efficient polymer electrolyte membrane fuel cells (PEMFCs). Most previous studies of dealloyed Pt alloys focused on the structure and mechanism of dealloyed Pt–Cu bimetallic materials. Also, stability concerns related to Cu prompted the search for alternative non-noble metal components for dealloying. Here, we report on a comparative study of dealloyed binary PtM 3 (M = Co, Cu, Ni) electrocatalyst for use in PEMFC cathodes. We also study synergistic effects of a third metal in ternary PtNi 3M (M = Co, Cu, Fe, Cr) cathode electrocatalysts. All catalyst precursor materials were prepared by an impregnation, freeze-drying, annealing route. After deployment of the catalyst precursor in single PEM cells, the active dealloyed form of the catalysts was obtained through a voltammetric dealloying protocol. Dealloyed binary PtM 3 catalysts showed more than a threefold activity improvement for ORR for M = Co , Cu, and close to a threefold improvement for M = Ni in terms of the Pt-mass activity ( A m g Pt − 1 ) of the single fuel cell, compared to a 45 wt% Pt/C reference cathode catalyst. Improvements in specific surface area normalized activities ( A c m Pt − 2 ) followed those in Pt-mass activity. All ternary catalysts, except the Fe containing one, showed clearly improved catalytic ORR performance compared to PtNi 3, in particular PtNi 3Co and PtNi 3Cu. A previously unachieved four- to fivefold activity improvement in real single MEAs was observed. Near-surface (XPS) and bulk (EDS/ICP) compositional characterizations suggested that the degree of dealloying of Pt–Co and Pt–Ni binary precursors is lower than that of Pt–Cu compounds. Pt–Co and Pt–Ni still showed 15–20 at.% non-noble metal near the surface and in the bulk of the dealloyed particles, whereas, under the chosen dealloying conditions, Pt–Cu formed core–shell structures with a Pt-rich surface and a Pt–Cu core. Of the selectively characterized Pt–Ni–Co and Pt–Ni–Cu ternaries, the near-surface composition of dealloyed Pt–Ni compounds showed an atomic ratio of about 1:1, compared to about 5:1 in the bulk, pointing to a Ni enrichment at the surface with only small residual amounts of Co or Cu. Our study highlights a number of novel active cathode catalyst compositions and underscores the sensitive dependence of the ORR activity of dealloyed Pt binary and ternary nanoparticle electrocatalysts on the nature and initial composition of the non-noble alloy component.

Synthesis of porous CuO–CeO2 nanospheres with an enhanced low-temperature CO oxidation activity

CuO-CeO2 nanospheres with a porous structure were synthesized by an improved urea method involving first hydrothermal treatment to get Ce-Cu binary precursor and then the calcination of the precursor. The CuO-CeO2 nanospheres consist of spherical particles with diameters in the range of 300-400 nm. These nanospheres are actually composed of nanoparticles of ca. 10 nm, resulting in the formation of a mesoporous structure. Compared with conventional urea method, in which Ce-Cu binary precursor is commonly achieved in an oil bath at appropriate temperature, the Ce-Cu binary precursor obtained via the hydrothermal process could be more highly homogeneous and more highly interdispersed CuO-CeO2 thus was formed. In addition, the resulted porous CuO-CeO2 catalyst has a lower CO oxidation temperature of as low as 71 °C.

Heteroatomic Deltahedral Zintl Ions of Group 14 and their Alkenylation

Reported is the synthesis of Ge(9-x)Sn(x) heteroatomic deltahedral Zintl ions and their alkenylation by reactions with alkynes. The nine-atom clusters are made either by extraction from mixed Ge/Sn precursors with nominal composition K(4)Ge(9-x)Sn(x) or by dissolution of mixtures of the corresponding binary precursors K(4)Ge(9) and K(4)Sn(9) in solvents with high dielectric constants such as DMF, DMSO, and acetonitrile. Reactions of the heteroatomic clusters with alkynes such as Me(3)SiC[triple bond]CSiMe(3), HC[triple bond]CCpr (Cpr = cyclopropyl), and HC[triple bond]CPh in ethylenediamine resulted in the following structurally characterized compounds with alkenylated heteroatomic clusters: [K-(2,2,2-crypt)](3)[GeSn(8)-CH=CH(2)].en.tol (1), triclinic, P1, a = 13.9220(3) A, b = 14.9788(3) A, and c = 21.5892(5) A, alpha = 94.2580(10) degrees , beta = 98.5210(10) degrees , and gamma = 98.4890(10) degrees , V = 4382.31(16) A(3), Z = 2; [K-(2,2,2-crypt)](4)[Ge(2)Sn(7)(CH=CH(2))(2)](2).en (2), monoclinic, P2(1)/c, a = 48.1883(15) A, b = 12.1551(4) A, and c = 21.4824(7) A, beta = 90.052(2) degrees , V = 12583.0(7) A(3), Z = 4; [K-(2,2,2-crypt)](3)[GeSn(8)-CH=CHCpr].en (3), monoclinic, P2(1)/c, a = 17.9132(9) A, b = 22.7967(11) A, and c = 21.6922(12) A, beta = 98.409(2) degrees , V = 8763.0(8) A(3), Z = 4; [K-(2,2,2-crypt)](3)[Ge(2)Sn(7)-CH=CHPh].2en (4), monoclinic, P2(1)/n, a = 13.2583(5) A, b = 47.0565(17) A, and c = 15.9978(6) A, beta = 111.536(2) degrees , V = 9284.1(6) A(3), Z = 4. The potassium countercations of the divinyl-substituted cluster in 2 were exchanged for tetrapropylammonium cations, and the resulting compound was also crystallized and structurally characterized: [Pr(4)N](4)[Ge(2)Sn(7)(CH=CH(2))(2)](2) (5), triclinic, P1, a = 11.6757(8) A, b = 18.8150(16) A, and c = 21.0608(17) A, alpha = 112.327(3) degrees , beta = 91.550(3) degrees , and gamma = 91.892(3) degrees , V = 4273.5(6) A(3), Z = 2. All clusters were also characterized in solution by electrospray mass spectrometry.

Low-temperature fabrication of BaBi2Nb2O9 ceramics by reaction controlled sintering

Reaction controlled sintering was applied to the fabrication of BaBi2Nb2O9 (BBN) ceramics at lower temperature. A powder mixture of BaCO3 and Nb2O5 was heated at 600 °C in a 1st step calcination to produce a binary precursor of BaNb2O6. The pre-heated powder was then mixed with a fixed amount of Bi2O3, which was subsequently pressed into a disk pellet. After a powder compact of the mixture was subjected to heating at 950 °C for 4 h, a BBN bulk sample with a relative density of 92% was successfully obtained. The low-temperature fabrication of dense BBN ceramics could be attributed to the inhibited formation of an intermediate phase of Ba5 Nb4O15 and the production of submicron powder with an appropriate reactivity during a 1st step calcination.

A One-Step Mechanochemical Route to Core−Shell Ca2SnO4 Nanoparticles Followed by 119Sn MAS NMR and 119Sn Mössbauer Spectroscopy

Calcium stannate (Ca2SnO4) nanoparticles with an average size of about 15 nm were synthesized via single-step mechanochemical processing of binary oxide precursors at room temperature. High-resolution TEM studies revealed a nonuniform structure of mechanosynthesized Ca2SnO4 nanoparticles consisting of an ordered core surrounded by a disordered surface shell region. The inner core of a Ca2SnO4 nanoparticle possesses a fully ordered orthorhombic structure, and the surface shell exhibits the thickness of about 1.5 nm. The volume fraction of surface shell regions in the nanostructured mechanosynthesized stannate is estimated to be about 50%. Because of the ability of both solid-state 119Sn MAS NMR and 119Sn Mössbauer spectroscopies to probe the local environment of Sn nuclei, valuable complementary insight into the local structural disorder in mechanosynthesized Ca2SnO4 was obtained. It was concluded that the near-surface layers of stannate nanoparticles are disordered because of broadly distorted geometry of SnO6 octahedra. The octahedra are deformed in such a way that they become more regular.

In‐situ XRD on formation reactions of Cu2ZnSnS4 thin films

AbstractStarting from stacked binary sulphide precursor layers with copper‐ and zinc‐rich composition the formation of Cu2ZnSnS4 (kesterite) has been investigated. Precursors with different layer thicknesses were deposited to evaluate the influence of material transport on the reaction kinetics. During annealing experiments the formation of kesterite in the different precursors was monitored by in‐situ energy‐dispersive X‐ray diffraction. An evaluation of the reaction rates revealed that at a temperature of 500 °C a kesterite film of 2 μm thickness can be formed within few minutes. The long annealing times reported in literature for well‐performing kesterite photovoltaic absorbers do therefore not owe to a general kinetic limitation for the formation of kesterite thin films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

EPR, μ -Raman and Crystallographic properties of spinel type ZnCr2O4

Structural, vibrational and electron paramagnetic resonance (EPR) analysis for compound ZnCr2O4 are shown in this work. These types of materials are used in technological applications as humidity sensors and piezoelectric devices. The compound was obtained by mean of solid state reaction technique from binary precursors ZnO and Cr2O3. After three thermal treatments the sample structure was monitoring using X ray diffraction (XRD), the spinel cubic phase has been indexed within O7h(Fd3m) spatial group. It is observed normal spinel phase. Micro-Raman analysis revealed bands for normal vibration modes of Zn and Cr atoms in tetrahedral and octahedral environments formed by oxygen atoms at approximately 400 and 900 cm-1, respectively. Bands around 941 cm-1 are associated possibly to vacancies in the tetrahedral and octahedral sites due to interaction between Zn and Cr ions. EPR signal from 150 to 300 K isothermals indicates a transition between inverse spinel to normal spinel type in a central field around 3350 G. A signal at approximately 3400 G corresponding to the C'r+3 in tetrahedral sites is observed near the central field.