Properties Of Silicides Research Articles

Electrochemical production of zirconium silicides from KCl–K<sub>2</sub>SiF<sub>6</sub>–ZrO<sub>2</sub> melt

The unique properties of zirconium silicides attract the attention of a large number of authors from various scientific fields. Expansion of application methods also poses the challenge of developing new, more environmentally friendly and affordable methods of production. The most environmentally friendly method without equipment requirements is the electrolysis of the molten salt. The work proposes a method for producing zirconium silicides by electrolysis of the KCl–K2SiF6–ZrO2 melt. In order to substantiate the electrolysis parameters, the kinetics of cathodic reduction was studied and the limiting stage of the process was determined. The structure and phase composition of the cathode deposit were studied using X-ray diffraction and electron scanning microscopy. In the course of the work, conclusions were drawn about the change in the content of the ZrO2 additives on the morphology of the sediment, and it was also suggested that it was possible to obtain zirconium silicides from more accessible raw materials, such as zircon.

Influence of Atomizing Gas Pressure on Microstructure and Properties of Nickel Silicide Intended for Additive Manufacturing

Influence of Atomizing Gas Pressure on Microstructure and Properties of Nickel Silicide Intended for Additive Manufacturing

First-principles investigation of physical properties of transition metal-based ternary TM5Si3C (TM = Nb, Mo, Ta, W) silicides of nowotny phase

In this work, the structural, electronic, mechanical, elastic anisotropy, thermodynamic, and optical properties of TM5Si3C silicides have been examined using first-principles calculations. All studied silicides fulfill the structural stability criteria. Computed mechanical properties reveal the ductile nature of Mo5Si3C, Nb5Si3C, and W5Si3C silicides, while Ta5Si3C silicide is brittle in character. Elastic anisotropy plots, including 2D and 3D, show highly anisotropic behaviour. The ascertained electronic and dielectric properties substantiate the conductive nature of all these silicides. All silicides in the visible region have an average reflectivity of 46 %, making them ideal for coatings to reduce solar heating. Debye temperature, melting point, thermal conductivity, and Gr u¨ neisen constant has also been investigated in current work. Thermodynamic properties have been computed at different pressure and temperature values including bulk modulus (B), volume (V), thermal expansion coefficient (α), Debye temperature (θD), and lattice heat capacity (Cv). The probed results of TM5Si3C ternary silicides demonstrate their viability for applications at elevated temperatures and as well as solar reflectors. Our findings may provide a gateway for exploring new ternary silicides and can act as an efficient, cost-effective guide for experimentalists.

The lattice vibration, mechanical anisotropy, stress-strain behavior and electronic properties of ZrxCuySiz intermetallics: A first-principles study

In recent years, ternary metal silicides have attracted more and more interests because of their excellent physical and chemical properties. The mechanical properties, electronic structures and thermal properties of ZrCuSi, ZrCuSi2, Zr3Cu4Si2, Zr3Cu4Si4 and Zr6Cu8Si12 ternary silicide were calculated by first-principles methods. The formation enthalpies, phonon dispersions and single-crystal elastic constants reveal that ZrCuSi, ZrCuSi2, Zr3Cu4Si2, Zr3Cu4Si4 and Zr6Cu8Si12 are thermodynamically, dynamically and mechanically stable. According to the analysis of the enthalpy of formation, ZrCuSi is the most thermodynamically stable intermetallics. Besides, Push's ratio (BH/GH), Poisson's ratio v, hardness and elastic anisotropic were investigated. The results indicated that ZrxCuySiz intermetallics show brittle properties and elastic anisotropy. Cu–Si bonds can be formed in ZrxCuySiz intermetallics due to the strong hybridization between Cu-3d and Si-3s states. The analysis of the electronic properties confirms that ZrxCuySiz intermetallics show the metallic behavior. The stability and mechanical properties are further explained by Debye temperature and electronic properties.

Main properties of silicides of the Mo - Si system

Using magnetron-ion sputtering, a layer of metallic molybdenum 1–2 μm thick was deposited on the surface of a silicon single crystal grown by the Czochralski method in an atmosphere of an inert argon gas at ambient temperature. According to the results of the experiment, pure Mo layers 2 μm thick deposited by magnetron reactive sputtering from a highly pure metal molybdenum target onto a cold silicon wafer substrate with a thickness of 1.5 mm. They have simultaneously high conductivity and transparency only in the case when a strictly defined deposition rate of molybdenum metal corresponds to a given partial pressure of argon in the volume. The sputtered targets are disks 40 mm in diameter with a thickness of 3-4 mm. The technological cycle of product processing includes the stage of target cleaning. Sputtering of a metal Mo target in pure argon Ar without the addition of oxygen promotes the formation of opaque metal films with very good conductivity. X-ray diffraction analysis of silicon monocrystals with a Mo metal-coated surface revealed compounds Mo3Si and MoSi0.65 in the molybdenum-silicon system. Silicon silicide MoSi2 was found to undergo an allotropic transformation in the temperature range 1850 ÷ 1900 °C, and the low- temperature variety α-MoSi2 has a tetragonal structure. The high- temperature form of β-MoSi2 has a hexagonal structure. The results of the study with an atomic scanning microscope showed that the chains of silicon atoms, connecting with Mo atoms, form zigzags passing through the prisms of the Mo structure along parallel X and Y axes.

Tailoring the electronic properties of nickel silicide by interfacial modification

Tailoring the microstructures to obtain metal silicide with low resistance and silicide monophase structure is a critical issue in integrated circuits manufacturing. In this work, the effect of introducing Pt insertion on the electronic properties and microstructure of the 9 nm NiPt thin film deposited by magnetron sputtering was studied. By introducing a thin Pt interlayer between the NiPt film and the substrate Si, the sheet resistance of the film can be effectively tuned. The results show that the sheet resistance of the film decreased from 27.6 to 14 Ω/sq, indicating that electrical performance has been enhanced about 1 times with Pt insertion introduced. The results show that the sheet resistance of the NiPt film with Pt insertion was lower and the phase composition of NiPt and Si presents a lower resistance NiSi phase than that of the NiPt without Pt insertion, and the sheet resistance of the film can be further reduced and the NiSi phase structure can be optimized. X-ray diffraction result shows that the phase composition of the NiPt film with Pt insertion presents a lower resistance NiSi phase than that of the NiPt without Pt insertion. Moreover, x-ray electron spectroscopy reveals that Pt insertion can reduce the diffusion of Ni into silicon effectively, which is beneficial to the formation of the monophase structure. In addition, x-ray reflectivity analysis showed that the Pt insertion further improved and modified the interface structure of nickel silicide, resulting in a smoother interface and improved electrical properties. These findings provide useful guidance for tuning the properties of the nickel silicide and also clarify the interface effect in the metal silicide materials.

Exploring of the structural stability, mechanical, electronic and optical properties of hydrogenated RE5Si4 (RE=Sc and Y) from first-principles calculations

In order to expand the applications of rare-earth ultrahigh-temperature materials, the overall performances including the hydrogenated mechanism, mechanical and optical properties of hydrogenated RE5Si4 (RE = Sc and Y) were explored and discussed by the first-principles calculations. It provides the theoretical support for the development and application of RE5Si4 silicides. Three hydrogenated models were considered based on the structural properties of RE5Si4 silicides. The results illustrate that the hydrogenated RE5Si4 are thermodynamically stable for the reason of the electronic interaction between hydrogen and RE5Si4 (RE = Sc and Y). Moreover, the elastic modulus and elastic constants demonstrate that the hydrogenated RE5Si4 display the worse mechanical properties than parent RE5Si4. Additionally, the doped H (2) models for Y5Si4 display the ductile behavior. The electronic structures show that all hydrogenated models possess metallic properties. And the stability of hydrogenated models and the localized hybridization between RE5Si4 and hydrogen atoms are closely related. Finally, the adsorption spectrum confirms that the hydrogen atomic doping improves the electronic jump between the occupied states and the empty states.

Exploring the electronic, mechanical, anisotropic, and optical properties of ternary silicides TM2Si2Ys (TM = Cu, Ir, Os, Pt, Pd, Rh, Ru) from a first principles investigations

AbstractIn recent years, the rare earth metal silicon‐based materials have attracted much attention. In order to accurately comprehend the application of rare earth silicides, we investigated the physical properties of the tetragonal TM2Si2Ys (TM = Cu, Ir, Os, Pt, Pd, Rh, Ru), orthogonal SiY, hexagonal Si2Y, and Si3Y5 compounds. The structural stability, electronic properties, elastic anisotropy, and optical properties of these silicides are investigated using the first‐principles calculations. The enthalpy of formation and phonon dispersions confirm that the binary and ternary silicides display the structural stability. According to the electronic structure, the stability, and mechanical properties of these silicides can be better understood. Ir2Si2Y has the stronger resistance to deformation and higher hardness. The values of v and G/B ratio confirm that Os2Si2Y, Pd2Si2Y, Pt2Si2Y, Ru2Si2Y, Rh2Si2Y, and Si2Y are the ductile materials. The 3D surface constructions and 2D projections of Young's modulus display the elastic anisotropy properties of the ternary silicides. The optical properties indicate that these silicides can be used as UV shielding materials for optical devices.

Electride properties of ternary silicide and germanide of La and Ce

We present a theoretical study of the electronic, spectral, and magnetic properties of ternary $RE\mathrm{ScSi}$ and $RE\mathrm{ScGe}$ $(RE=\mathrm{La},\mathrm{Ce})$ compounds based on the $\mathrm{DFT}+\mathrm{DMFT}$ method combining Density Functional Theory with Dynamical Mean-Field Theory. In this work, we find that Ce-based compounds, similar to LaScSi, exhibit electride-like features. Our calculations reveal that not only silicide $RE\mathrm{ScSi}$ compounds, but also their germanide $RE\mathrm{ScGe}$ analogs, exhibit high interstitial density characteristic of electrides. Remarkably, we find that both rare-earth $5d$ and scandium $3d$ contribute electrons to the strongly localized interstitial electron density, which can be considered as an electride anion with pronounced $s$ symmetry. In addition, we show that the Ce-based compounds show effects of strong electronic correlations in the $4f$ shell of cerium ions and strongly resemble those of $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{Ce}$.

Effect of Nickel Silicide Content on the Friction Properties of Wet Sintered Friction Material

The effect of nickel silicide on the friction properties of Cu-based wet sintered friction materials was investigated. The microstructure and mechanical properties of nickel silicide added Cu-based wet sintered friction materials were examined. Nickel silicide was prepared by mechanically alloying Ni and Si powder. Three types of Cu-based wet sintered friction materials with different nickel silicide contents (0 wt%, 5 wt%, 10 wt%) were fabricated by the powder metallurgy route. The phase transformation of Ni2Si to Ni31Si12 was observed in nickel silicide after a sintering process. The friction coefficient and wear rate decreased with increasing nickel silicide content. The wear scar changed from ploughing to micro-cutting with increasing nickel silicide content. As a result, it is suggested that nickel silicide can be used as a friction modifier when added to Cu-based wet sintered friction materials.

Improved Thermoelectric Properties of Fe Doped Si-Rich Higher Manganese Silicide

Improved Thermoelectric Properties of Fe Doped Si-Rich Higher Manganese Silicide

Selective synthesis and magnetic properties of iron silicide (Fe3Si and FeSi) at low temperature

Iron silicide (Fe3Si and FeSi) particles have been selectively synthesized through a solid-state reaction route.

Electronic States and Optical Properties of Silicides with Unique Arrangements of Si Atoms

Electronic States and Optical Properties of Silicides with Unique Arrangements of Si Atoms

Impact of the pre amorphization by Ge implantation on Ni0.9Pt0.1 silicide

The impact of the Pre Amorphization by Ge Implantation (PAI) on Ni0.9Pt0.1 silicide is studied. Reactions between a 10 nm thick Ni0.9Pt0.1 film and Si (100) substrate are analyzed as a function of the induced amorphous-Si thicknesses. In view of being compatible with the integration constraint of the 28 nm CMOS technologies, the Ge implantation dose is fixed at a low level. The relative position of the amorphous-Si/crystalline-Si interface and the silicide growth front is defined for each sample. Then, in-situ XRD analyses, X-Ray Reflectometry (XRR) and Sheet resistance (Rs) measurements are achieved to provide a deep study of silicide growth kinetics and silicide properties. First, a clear relationship is established between the silicide growth rate and the amorphous-Si thickness. Secondly, an easier NiSi nucleation and a decrease of its resistivity is observed when NiSi nucleates at the θ-Ni2Si/a-Si interface. These observations are discussed considering the impact of the amorphous-Si layer on the driving force, the nucleation barrier, the lateral growth rate, and NiSi roughness.

The effects of vacancies defects and oxygen atoms occupation on physical properties of chromium silicide from a first-principles calculations

In present work, the effects of vacancy defects on the mechanical and thermodynamic properties of Cr5Si3 have been investigated using the first-principles. The occupation mechanism of oxygen atoms in Cr5Si3 is also carefully analyzed and discussed. The vacancy formation, lattice vibrations, electronic structure, elasticity and thermodynamic parameters of Cr5Si3 were calculated separately. The results show that Cr5Si3 is stable and irrespective of the presence of vacancies or oxygen atoms occupation in it. In addition, the Si vacancies cause Cr5Si3 to undergo a brittle to ductile transition, which originates the weak hybridization between Cr and Si atoms. Importantly, when the Si-Va2 vacancy is occupied by oxygen atom, Cr5Si3 undergoes a brittle to ductile transition despite its poor hardness and resistance to deformation, which is attributed to the formation of weak Cr–O bonds. Furthermore, both the presence of vacancy defects and the introduction of oxygen atoms result in Cr5Si3 exhibiting the greater phase stability and better thermal properties.

Role of hydrogen on the structural stability, mechanical and thermodynamic properties of the cubic TM3Si silicides

Although the TM3Si silicides play an important role in transition metal silicides high-temperature materials, the hydrogenated mechanism of the cubic TM3Si is entirely unclear. To explore the hydrogenated mechanism, in this work, we apply the first-principles calculations to study the influence of hydrogen on the structural stability, mechanical and thermodynamic properties of TM3Si silicides. Based on the structural characteristic, four TM3Si silicides (Mo3Si, Nb3Si, Cr3Si and W3Si) and three hydrogen occupied models were considered. In particular, the influence of hydrogen on the stability, elastic properties, hardness, brittle-or-ductile behavior and Debye temperature of TM3Si was investigated. The result shows that the hydrogen is a thermodynamic stability in TM3Si because of the electronic interaction between hydrogen and TM3Si silicides. The thermodynamic stability of the hydrogenated TM3Si follows the order of Nb3Si<Cr3Si<Mo3Si<W3Si. Importantly, it is found that the hydrogen weakens the elastic properties and hardness of TM3Si because the introduction of hydrogen reduces the electronic interaction between TM atom and Si atom. On the contrary, the hydrogen improves the ductile behavior of TM3Si silicides. In addition, the hydrogen reduces the Debye temperature of TM3Si silicides.

First-principles study of the lattice vibration, elastic anisotropy and thermodynamical properties of Tantalum Silicide with the different crystal structures

TaSi2 is the ultra-high-temperature ceramic material, the intrinsic brittleness hinders its high temperature applications. We design five possible structures (Cmcm-type, FdddZ-type, I4/mmm-type and P6222-type and P4332-type structures) by means of first-principles calculations. The structural influence on their lattice vibration, mechanical, electronic and thermal properties were investigated. Except for P4332-type structure, the rest of potential structures are structurally stable. Meanwhile, the I4/mmm-type structure presents the largest hardness among the four structures. As for the anisotropic features, P6222-type structure TaSi2 can be the potential isotropic material and Cmcm-type structure has the relatively obvious anisotropic features in consideration of the anisotropic indexes and the directional dependence of Young's modulus. The electron properties for the four possible structures were discussed by the PDOS and TDOS curves. The thermal behavior of Cmcm-type and FdddZ-type structures are similar in results, and exhibits the nearly coincident curves of the Debye temperature, heat capacity, entropy and enthalpy.

Investigation of the structural stability, mechanical, and thermodynamic properties of Hf5BSi3 silicide with vacancies defects

In recent years, ternary silicides have attracted more and more attentions. Hf5BSi3 high temperature material has been synthesized. Nevertheless, the inherent brittleness affects its industrial applications. In present work, the effects of the vacancies on the structural stability, elastic constants and thermodynamic properties of Hf5BSi3 are clarified by first-principles calculations. The values of vacancy formation energy illustrate the structural stability of Hf5BSi3 with atomic vacancies. These vacancies weaken the shear and volume deformation resistance of Hf5BSi3, but well improve the brittle behavior of Hf5BSi3 with the larger values of B/G. The structural stability and mechanical behavior of Hf5BSi3 with vacancies are analyzed by the density of states and electron density difference. The thermal parameters exhibit the influence of the vacancies on the thermodynamic properties of Hf5BSi3 at elevated temperature.

Crystal stabilities and electronic properties of thorium silicide under ambient conditions and high pressures from a first-principles study

The thorium compounds are prospective candidates for the next generation nuclear materials. Using the first-principles and particle swarm optimization methods, we have investigated structures and physical properties of four atomic ratios of thorium and silicon hybrids under various ranges from ambient pressure to 200 GPa. A series of new phases have been predicted and thermodynamics, mechanical stabilities, elastic properties, electronic properties and chemical bonds of all the stable structures have been studied in details. Furthermore, we utilize potential energy surface to investigate the vibration property of Si2 dimer in Th3Si2. The result indicates that the Si2 dimer in Th3Si2 compound have the similar vibration property as a free standing Si2. This also means the silicon atoms do not have a strong interaction with thorium atoms in thorium silicide.

The vacancy defects and oxygen atoms occupation effects on mechanical and electronic properties of Mo5Si3 silicides

Improving brittle behavior and mechanical properties is still a big challenge for high-temperature structural materials. By means of first-principles calculations, in this paper, we systematically investigate the effect of vacancy and oxygen occupation on the elastic properties and brittle-or-ductile behavior on Mo5Si3. Four vacancies (Si–Va1, Si–Va2, Mo–Va1, Mo–Va2) and oxygen occupation models (O–Mo1, O–Mo2, O–Si1, O–Si2) are selected for research. It is found that Mo–Va2 vacancy has the stronger structural stability in the ground state in comparison with other vacancies. Besides, the deformation resistance and hardness of the parent Mo5Si3 are weakened due to the introduction of different vacancy defects and oxygen occupation. The ratio of B/G indicates that oxygen atoms occupation and vacancy defects result in brittle-to-ductile transition for Mo5Si3. These vacancies and the oxygen atoms occupation change the localized hybridization between Mo–Si and Mo–Mo atoms. The weaker O–Mo bond is a contributing factor for the excellent ductile behavior in the O-Si2 model for Mo5Si3.