Substitution Of Germanium Research Articles

The Effect of Partial Substitution of Ge-S-Cd Alloys on the Density of Energy States

Five samples of the ternary alloy Ge-S-Cd were created using the melting point method, and the effects of partially substituting cadmium for germanium were determined. and partial substitution of germanium by cadmium was used to study the change in electrical conductivity. Electrical experiments were performed on Ge35-xS65Cdxternary alloy with x = 0, 5, 10, 15, and 20. It was discovered that the conductivity (σdc) rises with rising temperature in all samples under experiment. This confirms that the samples have semiconductor behavior. It has been observed that there are three regions of electrical conductivity in the electrical conductivity curve at low, moderate, and high temperatures. The preexponential elements and effective energies of each of the three conduction regions were calculated for each of the Cadmium values. It was found that all of them were impacted by a rise in the value of cadmium in the ingot. A numerical analysis of the conductivity equation was also performed to calculate the energy of the expanding states' density in local states and at the Fermi level. It has been observed that all of the values of samples change with the rising value of cadmium concentration.

Fast Lithium Ion Conductivity in the Solid Solution Li8+X Al X Ge1-X P4 (0≤X≤1) By Aliovalent Substitution

All solid-state batteries are considered to extend the limits of lithium ion batteries in terms of power density, cycle life stability and device safety. One key component for this technology is the solid electrolyte. Heavy research on oxide and sulfide based lithium ion conductors has brought out some highly optimized systems, which show ionic conductivities up to 25 mScm-1.[1] Recently lithium phosphides have been introduced as a new class of lithium ion conductors with ionic conductivities of 1.1 mScm-1 for Li14SiP6 [2] and 3 mScm-1 for Li9AlP4. [3] Due to the increased negative charge of the phosphide anion compared to conventionally used chalcogenide anions, the lithium content and therefore the charge carrier concentration is significantly higher. Since aliovalent doping can lead in sulfides to an ionic conductivity an order of magnitude higher than the parent undoped compounds, we aim here for the stepwise aliovalent substitution of the four-valent tetrel-ion in lithium phosphido-tetrelates with three-valent aluminum, to further increase the lithium concentration as well as the volume of the unit cell.[5][6] In this work we show the effect of the substitution of germanium by aluminum on the ionic conductivity in the solid solution Li8+x Al x Ge1-x P4 (0≤x≤1). β-Li8GeP4,[4] Li9AlP4 and the solid solution Li8+x Al x Ge1-x P4 crystallize in the cubic space group P-43n with the phosphorus atoms building a distorted fcc-lattice. The solid solution strictly follows Vegard’s law showing a linear dependency of the lattice parameter on the substitution grade over the whole investigated range (figure 1). Ge and Al atoms occupy 1/8 of the tetrahedral voids. Remaining tetrahedral voids and some octahedral voids are partially occupied by lithium. The cubic structure makes the system a convenient model for investigations of substitution effects, as symmetry restrictions prohibit extent distortion. Lithium ions are mobile and migrate between face sharing octahedral and tetrahedral positions as well as edge sharing tetrahedral voids. Impedance spectroscopy measurements were conducted in a custom-made cell setup for powder samples, where powders are pelletized in situ and contacted by steel electrodes. High pressure is applied over six screws, tightened with defined torque. The temperature was controlled by a specially designed heating block connected to a heating circulator, which allows to do all measurements in argon atmosphere. The ionic conductivity in Li8+x Al x Ge1-x P4 increases with the amount x of aluminum by nearly one order of magnitude. This increase does not proceed linearly, revealing a more complex correlation (figure 1). Figure 1: Left: Vegard plot for the solid solution Li8+x Al x Ge1-x P4 (0≤x≤1) created on powder X-ray diffraction data. The black line acts as a guide to the eye, emphasizing the linear dependency of the lattice parameter a on the grade of substitution x. The upper left corner shows the crystal structure of Li8+x Al x Ge1-x P4. Right: Temperature dependency of the ionic conductivity for different compositions of Li8+x Al x Ge1-x P4.

Influence of diffusion processes on structure of brazed joints and brazing filler metal after spreading over Ni3Al-based alloy

This paper presents the results of investigations on wetting with Pd-Ni-Cr(Me)-Ge system brazing filler metal of pure nickel, high-temperature alloy based on nickel aluminide (Ni3Al). Micro-X-ray spectrum examinations showed that spread of Pd-Ni-Cr(Ме)-Ge system brazing filler metal over pure nickel substrate, which has no aluminum, promoted crystallization of brazing filler metal in the form of a solid solution of palladium-nickel and single disperse inclusions of (PdNiCr)-14,13Ge phase. This inclusion precipitates along the boundaries of solid solution grains and can be the reason for strengthening phase. In the spread of this alloy over Ni3Al (Ni-Al-Mo-В)-based high-temperature alloy, containing around 10 wt.% of aluminum, there is another composition and morphological structure of brazing filler metal after crystallization. Thus, the solid solution crystallizes on the base metal substrate. Phase precipitations based on palladium (60.59%) saturated with aluminum (12.3%) is formed in it. In brazing of Ni3Al (Ni-10Al-14Mo-В)-based alloy using this brazing filler metal, the high concentration of aluminum in base metal and the presence of concentration gradient at interface result in active diffusion of the latter from base metal in the brazed seam. Diffusion processes lead to the substitution of germanium on aluminum in (PdNiCr)xGey phase. It results in the formation of (PdNiCr)xAly intermetallic phase, the concentration of aluminum which corresponds to the concentration of aluminum in base metal and it precipitates in a central zone of the brazed seam and leads to brittle fracture of the brazed joints. The use of the brazing filler metal on the Ni-Cr-Al-Me for brazing of nickel aluminide leads to the formation of a structure without intermetallic phases and eutectics in the central zone of the brazed seam.

The influence of germanium ions on the infrared long persistent phosphor Zn1+xAl2-2xGexO4: Cr

Germanium substitution in the original ZnAl2O4:Cr3+ infrared long persistent phosphors Zn1+xAl2-2xGexO4: Cr (x = 0.1, … 1) were synthesized via a high temperature solid state reaction. X-ray diffraction (XRD), afterglow decay curves, photoluminescence, and isometric thermoluminescence spectra were collected to characterize these samples. With the increase of substitution of germanium, the diffraction peaks shift to the shorter angles and the phase of Zn2GeO4 appears (x ≥ 0.5) as indicated by the X-ray diffraction results. Photoluminescence shows the infrared emissions of Cr3+ response, and consistently confirms that Cr3+ is very sensitive to the host crystal field in this material. A spinel structure is indicated for the Cr3+ infrared emission. However, the substitution of germanium can not only modify the host structure, but also provide defects which improve the afterglow of the materials as indicated by the thermoluminescence (TL) results. With a suitable substitution of germanium, TL peaks move to lower temperatures and become broader, which are both good factors for the room temperature afterglow phosphors. All the results indicate that non-gallate material ZnAl2O4 Cr3+, with a suitable concentration of germanium substitution, could be an excellent infrared long afterglow phosphor.

One-Step, Catalyst-Free, Scalable in Situ Synthesis of Single-Crystal Aluminum Nanowires in Confined Graphene Space.

Nanowires have a wide range of applications, such as transparent electrodes, Li-ion battery anodes, light-emitting diodes, solar cells, and electronic devices. Currently, aluminum (Al) nanowires can be synthesized by thermally induced substitution of germanium (Ge) nanowires, chemical vapor deposition on other metal substrates, and template-assisted growth methods. However, there are still challenges in fabricating extremely high-purity nanowires, large-scale manufacturing, and simplifying the synthesis process and conditions. Here, we report for the first time that single-crystal Al nanowires can be one-step, in situ synthesized on a reduced graphene oxide (RGO) substrate on a large scale without using any catalysts. Through a simple high temperature treatment process, commercial micro-sized Al powders in RGO film were transformed into a single-crystal Al nanowire with an average length of 1.2 μm and an average diameter of 18 nm. The possible formation mechanism of the single-crystal Al nanowires is proposed as follows: hot aluminum atoms eject from the pristine aluminum/alumina core/shell structure of Al powders when they build up enough energy from the thermal stress under high temperature and confined space conditions, which is supported by both experimental and computational results. The method introduced here can be extended to allow the synthesis of one-dimensional highly reactive materials, like alkali metal nanowires, in confined spaces.

Correlating Transport and Structural Properties in Li1+xAlxGe2–x(PO4)3 (LAGP) Prepared from Aqueous Solution

Li1+ xAl xGe2- x(PO4)3 (LAGP) is a solid lithium-ion conductor belonging to the NASICON family, representing the solid solution of LiGe2(PO4)3 and AlPO4. The typical syntheses of LAGP either involve high-temperature melt-quenching, which is complicated and expensive, or a sol-gel process requiring costly organic germanium precursors. In this work, we report a simple method based on aqueous solutions without the need of ethoxide precursors. Using synchrotron and neutron diffraction, the crystal structure, the occupancies for Al and Ge, and the distribution of lithium were determined. Substitution of germanium by aluminum allows for an increased Li+ incorporation in the material and the actual Li+ content in the sample increases with the nominal Li+ content and a solubility limit is observed for higher aluminum content. By means of impedance spectroscopy, an increase in the ionic conductivity with increasing lithium content is observed. Whereas the lithium ionic conductivity improves, due to the increasing carrier density, the bulk activation energy increases. This correlation suggests that changes in the transport mechanism and correlated motion may be at play in the Li1+ xAl xGe2- x(PO4)3 solid solution.

Synthesis and Conductivity Study of Solid Electrolytes Li1 + xAl x Ge2–x(PO4)3 (x = 0–0.65)

A new liquid-phase method has been suggested for synthesis of solid electrolytes with lithium conductivity of composition Li1 + xAl x Ge2–x(PO4)3 (x = 0, 0.1, 0.3, 0.5, 0.6, 0.65) with a NASICON structure. The method is based on the use of an alkaline solution of GeO2 and water-soluble Al(NO3)3 · 9H2O, LiNO3, and (NH4)2HPO4 salts. The synthesized materials have been characterized by X-ray powder diffraction and impedance spectroscopy. The formation of crystalline Li1 + xAl x Ge2–x(PO4)3 products with a NASICON structure is observed at 750–1000°C depending on the degree of substitution of germanium by aluminum. The effect of final powder annealing temperature and ceramics sintering temperature on the phase composition, density, and conductivity of resulting materials has been studied. The material of composition Li1.6Al0.6Ge1.4(PO4)3 produced by sintering the synthesized powder at 900°C exhibits the highest conductivity (3.8 × 10–4 S/cm at a ceramics density of 86%) and the lowest conductivity activation energy (30.5 ± 0.4 kJ/mol in the temperature range 25–250°C).

Phase formation, microstructure, and ionic conductivity of (La,Sr)(Ga,Ge,Mg)O3–d ceramics

We have prepared ceramic (La0.8Sr0.2){[Ga0.8–x (Ge0.5Mg0.5) x ]Mg0.2}O3–d (LSGGM) (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8) samples by solid-state reactions and studied their phase composition, structure, microstructure, and electrical conductivity. Phase-pure solid solutions have been obtained upon substitution of germanium and magnesium cations for up to 20 at % of the gallium cations. The modified samples have been shown to have high density, optimal microstructure, densely packed grains, and high electrical conductivity at high temperatures.

Germanium Alloyed Kesterite Solar Cells with Low Voltage Deficits

It has previously been shown that substitution of germanium for tin in Cu2ZnSn(S,Se)4 provides a means to change the band gap. Here, we show that Ge substitution can also be used to improve carrier collection and decrease the open-circuit voltage deficit that has hindered kesterites. Using a simple molecular ink, we spray coat continuous composition gradients of Cu2Zn(Sn,Ge)(S,Se)4 spanning 0–90% Ge/(Ge + Sn). By mapping the absolute intensity photoluminescence and making devices from these gradients, we are able to clearly resolve changes in material properties and device performance with composition. We find that Ge can be used to increase the band gap as high as 1.3 eV (50% Ge/(Ge + Sn)) without any loss in optoelectronic material quality, but beyond 50% Ge/(Ge + Sn), the device efficiency decreases rapidly. We show evidence that the degradation results from both a deep defect located about 0.8 eV above the valence band and unfavorable band alignment. As the band gap increases, the defect moves toward ...

Cyclacenes and short zigzag nanotubes with alternanting Ge―C bonds: theoretical impacts of Ge on the ground state, strain, and band gap

[6]n Cyclacenes and short zigzag [6]n carbon nanotubes (n = 5–10) have unstable singlet open‐shell (Sos) ground states. We have boosted their stability by implementing altering Ge―C bonds that acquire Scs ground states with larger band gap (ΔELUMO–HOMO) at B3LYP and BPW91 levels of theory. Fascinatingly, homodesmic calculations indicated release of almost two folds of strain energy upon substitution of germanium for carbon. This may turn the green lights for synthesis of germanium–carbon cyclacenes and short zigzag nanotubes. Copyright © 2014 John Wiley & Sons, Ltd.

Interplay between crystal field splitting and Kondo effect in CeNi9Ge4−xSix

The pseudo-ternary solid solution CeNi9Ge4−xSix (0 ≤ x ≤ 4) has been investigated by means of x-ray diffraction, magnetic susceptibility, specific heat, electrical resistivity, thermopower and inelastic neutron scattering studies. The isoelectronic substitution of germanium by silicon atoms causes a dramatic change of the relative strength of competing Kondo, RKKY and crystal field (CF) energy scales. The strongest effect is the continuous elevation of the Kondo temperature TK from approximately 3.5 K for CeNi9Ge4 to about 70 K for CeNi9Si4. This increase of the Kondo temperature is attended by a change of the CF level scheme of the Ce ions. The interplay of the different energy scales results in an incipient reduction of the ground state degeneracy from an effectively fourfold degenerate non-magnetic Kondo ground state with unusual non-Fermi-liquid features of CeNi9Ge4 to a lower one, followed by an increase towards a sixfold, fully degenerate ground state multiplet in CeNi9Si4 (TK ∼ ΔCF).

Hydrothermal Growth and Structural Studies of Si1–xGexO2 Single Crystals

The substitution of germanium in the α-quartz structure is a method investigated to improve the piezoelectric properties and the thermal stability of α-quartz. Growth of α-quartz type Si(1-x)Ge(x)O(2) single crystals was performed using a temperature gradient hydrothermal method under different experimental conditions (pressure, temperature, nature of the solvent, and the nutrient). To avoid the difference of dissolution kinetics between pure SiO(2) and pure GeO(2), single phases Si(1-x)Ge(x)O(2) solid solutions were prepared and used as nutrients. The influence of the nature (cristobalite-type, glass) and the composition of this nutrient were also studied. Single crystals were grown in aqueous NaOH (0.2-1 M) solutions and in pure water. A wide range of pressures (95-280 MPa) and temperatures (315-505 °C) was investigated. Structures of single crystals with x = 0.07, 0.1, and 0.13 were refined, and it was shown that the structural distortion (i.e., θ and δ) increases with the atomic fraction of Ge in an almost linear way. Thus, the piezoelectric properties of Si(1-x)Ge(x)O(2) solid solution should increase with x, and this material could be a good candidate for technological applications requiring a high piezoelectric coupling factor or high thermal stability.

Raman scattering study ofα-quartz andSi1−xGexO2solid solutions

alpha-quartz-type Si1−xGexO2 solid solutions (x=0.06, 0.11, and 0.24) and pure SiO2 were investigated by Raman spectroscopy. Coupled and decoupled vibrational modes were identified at room temperature as a function of composition. Tetrahedral tilting librational modes involved in the displacive alpha beta-quartz phase transition are decoupled. The wave number of the coupled A1 mode located at 464 cm−1 for pure alpha-quartz was found to vary quite linearly with germanium content. Raman spectra were recorded up to 1473 K. Substitution of germanium in the quartz lattice clearly improves the thermal stability of the alpha phase. The alpha beta-quartz phase transition temperature increases from 846±1 K for x=0 to about 1300±50 K for x=0.24. At the same time, the dynamic disorder observed in quartz well below the transition is reduced in the solid solutions.

Effect of Ge Doping on Thermoelectric Properties of SryCo4Sb12-xGex

Skutterudite compounds, SryCo4Sb12-xGex (y=0.3, x=0–0.3), are synthesized by a melting method. The effect of germanium doping on thermoelectric properties is investigated. Electrical conductivity, Seebeck coefficient, and thermal conductivity are measured from 300 to 850 K. The substitution of germanium is effective in reducing thermal conductivity while keeping excellent electrical transport properties owing to the high filling fraction of Sr and Ge doping as charge compensation. The dimensionless thermoelectric figure of merit ZT is observed to increase from 0.9 at 850 K for Sr0.28Co4Sb12 to 1.05 for Sr0.34Co4Sb11.9Ge0.1 at 850 K. These results suggest that doping with germanium is an attractive avenue to optimization of filled skutterudites.

Effect of Ga substitution for Ge on magnetic and crystal properties of the GdMnGe 1− x Ga x intermetallics

The magnetic properties of the GdMnGe and the GdMnGe 0.5Ga 0.5 intermetallic compounds have been investigated by magnetization and susceptibility measurements in a broad temperature range for the purpose to explain the influence of the substitution of germanium by gallium on the magnetic and crystalline properties of the new ternary GdMnGe 0.5Ga 0.5 compound. The X-ray phase analysis and the metallographic analysis have shown: the orthorhombic TiNiSi-type structure and the hexagonal ZrNiAl-type structure for GdMnGe and for GdMnGe 0.5Ga 0.5, respectively. It was shown, that replacing Ga for Ge significantly influences the magnetic ordering. The GdMnGe displays a complex antiferromagnetic structures with phase transition temperature T 1=100 K and the Néel temperature equal to 350 K, as in turn the GdMnGe 0.5Ga 0.5 exhibits ferrimagnetic type behavior with T N=170 K.

The Substitution of Germanium for Silicon in AST‐Type Zeolite.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The substitution of germanium for silicon in AST-type zeolite

The substitution of silicon by germanium in the AST zeolite framework type, [Si n Ge 40− n O 80] ∗4(SDA +F −) expressed as unit cell content in its cubic F-centered symmetry, has been studied. Three different kinds of templates, dimethyldiethylammonium, dimethyldiisopropylammonium and isopropyltrimethylammonium cations, were used in the hydrothermal synthesis process in fluoride medium. The products were identified with XRD, MAS NMR, SEM and thermal analysis. The analysis of the X-ray powder diagrams shows that AST crystallizes in different space group symmetries depending on the nature of the SDA and the degree of Ge-substitution. The resonance signals of 19F in MAS NMR experiments for the pure Si- and Ge-end members are at −38.2 and ∼−15 ppm, respectively, indicating that the F −-anion is located as co-template in the double-four-ring (D4R) of the tetrahedral framework. This is confirmed by Rietveld analysis of powder diffraction data of the pure Ge-end member. The peak splitting of the 19F NMR signal in pure GeO 2AST-type material is related to the displacement of F − location inside the D4R. Two more distinct signals at ∼−8 and ∼−19 ppm, respectively, are observed for X-ray pure AST-samples of intermediate compositions and assigned to fluoride in D4R built of 4[GeO 4]- and 4[SiO 4]-tetrahedra (4Ge, 4Si) and to (2Ge, 6Si)-D4R, respectively. An ordered distribution of Ge in the AST-framework is proposed for cubic AST with compositions around Si/Ge=1.5–1 by correlating the intensities of 19F NMR signals and the results from chemical analysis. This model is further confirmed by the quantitative analyses of the corresponding 29Si MAS NMR spectra.

A zeolite with interconnected 8-, 10- and 12-ring pores and its unique catalytic selectivity.

One of the major goals in catalysis is to improve the capabilities of microporous materials. This can be accomplished by synthesizing new zeolites with controlled pore architectures. In particular, zeolites containing channels of different sizes in the same structure are desirable. Here, we report a zeolite containing fully interconnected 8-, 10- and 12-membered-ring pores, synthesized by combining the structure-directing effect of the organic 1,5-bis-(methylpyrrolidinium)-pentane and the framework isomorphic substitution of germanium for silicon. Analysis of the crystal structure determined by direct methods from synchrotron powder diffraction data reveals 16 independent tetrahedrally coordinated atoms. This thermally and hydrothermally stable zeolite structure, when synthesized in its acidic form by incorporating aluminium in the framework, presents unique catalytic shape-selectivity effects derived from its particular pore topology.

Na2Al2Ge3O10·2H2O: an aluminogermanate with the tetranatrolite topology

An aluminogermanate, Na2Al2Ge3O10·2H2O (NaAlGe-NAT), possessing the natrolite topology has been synthesized under hydrothermal conditions at 423 K from sodium- and tetramethylammonium-containing gels. Room temperature single crystal X-ray diffraction data indicate a tetragonal unit cell with a = 13.314(2) and c = 6.819(2) A, and space group . NaAlGe-NAT displays complete disorder of aluminium and germanium in the framework, with Ge/Al = 1.5. The substitution of germanium for silicon in the framework leads to a larger unit cell volume for NaAlGe-NAT compared with Na8Al8Si12O40·8H2O (NaAlSi-NAT) and Na8Ga8Si12O40·8H2O (NaGaSi-NAT) framework structures. The mean rotation angle Ψ of the chains (composed of 4=1 secondary building units) relative to the a and b cell axes is 20.4°, compared with 21.7 and 22.9° calculated for NaGaSi-NAT and NaAlSi-NAT, respectively. Elliptical channels along the c-axis host well-ordered water molecules and sodium cations in fully occupied sites.

Crystal Structure and Magnetic Properties of the Lanthanoid Platinum GermanidesLnPtGe (Ln=Ce, Pr, Nd, Sm)

The crystal structures of the title compounds were reinvestigated. The previously reported KHg2(CeCu2) type structure with statistical distribution of the platinum and germanium atoms corresponds only to the subcell of the ordered orthorhombic YPdSi type structure (Pmmn, Z=8) of these compounds, which was refined from single-crystal X-ray diffractometer data of CePtGe:a=445.0(1) pm,b=1464.8(3) pm,c=761.8(2) pm; PrPtGe:a=444.01(3) pm,b=1456.57(9) pm,c=761.71(5) pm; and the low-temper- ature (α) modification of SmPtGe:a=440.0(1) pm,b=1428.1(2) pm,c=756.6(1) pm. Nevertheless, some evidence for disorder was obtained from the refinement of the occupancy parameters of these compounds. The results suggest the substitution of germanium by platinum atoms and/or vice versa in the order of a few at%. The high-temperature (β) modification of SmPtGe with TiNiSi type structure was confirmed by a refinement from single crystal diffractometer data. The magnetic properties of these compounds were investigated with a SQUID magnetometer. CePtGe, PrPtGe, and NdPtGe follow the Curie–Weiss law with magnetic moments close to those of the trivalent rare earth elements. The magnetic properties ofα- andβ-SmPtGe are dominated by the Van Vleck paramagnetism of the samarium atoms. Antiferromagnetic ordering was detected for CePtGe, NdPtGe, and both modifications of SmPtGe with Néel temperatures between 4 and 6 K, while PrPtGe remains paramagnetic down to 2 K. The crystal structures of these compounds are briefly discussed together with those of the LaPtSi and LaIrSi type structures, which occur for LaPtGe and EuPtGe, respectively.