Concentration Dependence Of Lattice Parameters Research Articles

Phase equilibra in the Ag2S–Ag8GeS6–Ag8SiS6 system and some properties of solid solutions

Phase equilibria in the Ag2S–Ag8SiS6–Ag8GeS6 system were studied using differential thermal analysis and powder X-ray diffraction technique. Boundary section Ag8SiS6 – Ag8GeS6, liquidus surface projection, an isothermal section of the phase diagram at 300 K, and some polythermal sections of the studied system were constructed. The formation of continuous series of solid solutions between both crystalline modifications of the starting compounds was determined in the Ag8SiS6–Ag8GeS6 system. The liquidus surface of the Ag2S–Ag8SiS6–Ag8GeS6 system consists of two fields corresponding to the primary crystallization of the high-temperature modifications of the HT-Ag8Si1-xGexS6 and HTAg 2S phases. Lattice parameters for both modification of solid solutions were calculated based on powder X-ray diffraction data. The concentration dependence of lattice parameters obeys Vegard’s rule. The obtained new phases are of interest as environmentally safe materials with thermoelectric properties and mixed ionelectron conductivity

PHASE EQUILIBRIA IN THE Ag8SiTe6–Ag8GeTe6 SYSTEM

Phase equilibria in the Ag8SiTe6–Ag8GeTe6 system were experimentally investigated by means of differential thermal analysis and powder X-ray diffraction techniques. It was established that continuous series of solid solutions with SiGe substitution are formed in the system. T–x-diagram of the title system and concentration dependence of lattice parameters of the obtained solid solutions were plotted

Investigation of the Substituting Effect of Se on the Physical Properties and Performances of Cd〖Se〗_x 〖Te〗_(1-x)and Zn〖Se〗_x 〖Te〗_(1-x) Materials for Semiconductor Radiation Detectors

The structural and electronic properties of and semiconductor detectors at various concentrations x = 0, 0.25, 0.5, 0.75 and 1 of Selenium (Se) were determined by using the full potential-linearized augmented plane wave (FP-LAPW) based on the density functional theory (DFT). The compositional dependence of such properties was analysed and discussed. The concentration dependence of lattice parameter and bulk modulus show nonlinearity. All the investigated alloys have a direct bandgap (Γ-Γ) which decreasesnonlinearly with increase in Se concentration. On the other hand, Geant4 simulations have been performed for studying the absolute and full-energy peak detection efficiencies and energy resolution at 1.5”×1.5” of these alloys as semiconductor detectors in the 511-1332 keV gamma-ray energy range. Ours findings are in a good agreement with the available theoretical and experimental data. We hope that our results serve as are reference for future theoretical and experimental researches.

Synthesis, Structural and Electrical Studies of Li-Ni-Cu Nano Ferrites

Abstract Li-Ni ferrite has gained great scientific elicit owing to of its unparalleled properties and applications. The copper doped Li-Ni ferrite has been synthesized by sucrose method. The structure was characterized by X-ray diffraction, which has confirmed the formation of single-phase spinel structure. X-ray diffraction and FTIR data reveals the formation of cubic structure phase. Unit cell parameters vary with copper content; overall variation of the unit cell parameters obeys Vegard’s law. The main absorption bands of spinel ferrite have appeared through IR absorption spectra recorded in the range of 300–700 cm−1. The copper concentration dependence of lattice parameters obeys Vegard’s law. DC electrical resistivity of the prepared samples decreases with increasing in the temperature which shows the semiconducting behaviour of all nano ferrites. The most prominent influence copper doping on the electrical properties of Li-Ni ferrites has been reported.

Influence of doping of mercury atom(s) on optoelectronic properties of binary cadmium chalcogenides - A density functional theory based investigation with different exchange-correlation functionals and including spin-orbit coupling

Influence of doping of mercury atom(s) on optoelectronic properties of binary cadmium chalcogenides have been investigated theoretically by designing the mercury doped cadmium chalcogenide ternary alloys in B3 phase at some specific Hg-concentrations and studying their optoelectronic properties using DFT based FP-LAPW methodology. The structural properties are computed using WC-GGA, while spin-orbit coupling included electronic and optical properties are computed using TB-mBJ, EV-GGA, B3LYP and WC-GGA exchange-correlation functionals. In addition, electronic properties of mercury chalcogenides are calculated precisely using the GGA+U functionals. The concentration dependence of lattice parameter and bulk modulus of each of the HgxCd1−xS, HgxCd1−xSe, HgxCd1−xTe alloy systems show almost linearity. For each of the alloy systems, band gap decreases almost linearly with increase in Hg-concentration in the unit cell and contribution from charge exchange to the band gap bowing is larger than that from for each of the volume deformation and structural relaxation. Also, covalent bonding exists between different constituent atoms in each compound. Optical properties of each specimen are computed from their spectra of dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity, optical absorption coefficient and energy loss function. Several calculated results have been compared with available experimental and other theoretical data.

Effects of doping of mercury atom(s) on optoelectronic properties of binary zinc chalcogenides - A first principle based theoretical investigation

Effects of doping of mercury atom(s) on optoelectronic properties of diatomic zinc chalcogenides are investigated theoretically by designing zinc-mercury-chalcogenide ternary alloys in zinc-blende (B3) phase at some specific Hg-concentrations and studying their optoelectronic properties using DFT based FP-LAPW approach. The WC-GGA functional is used in computing structural properties, while the spin-orbit coupling included electronic and optical properties are calculated using TB-mBJ, EV-GGA, B3LYP and WC-GGA functionals. In addition, electronic properties of mercury chalcogenides are calculated precisely using the GGA + U functional. The concentration dependence of lattice parameter and bulk modulus of each of the HgxZn1−xS, HgxZn1−xSe, HgxZn1−xTe alloy systems show nonlinearity. For each of the alloy systems, band gap decreases nonlinearly with increase in Hg-concentration in the unit cell and contribution from charge exchange to the band gap bowing is larger than that from each of the volume deformation and structural relaxation. The atomic and orbital origin of electronic states in the band structure of each compound is explored from its DOS. Covalent bonding between different constituent atoms in each compound is observed. Optical properties of each specimen are computed from the spectra of dielectric function, refractive index, extinction coefficient, normal incidence reflectivity, optical conductivity, optical absorption coefficient and energy loss function. Several calculated results have been compared with available experimental and other theoretical data.

Structural analysis, magnetic and electrical properties of samarium substituted lithium–nickel mixed ferrites

A series of Sm-doped Li–Ni ferrites with formula of (Li0.5Fe0.5)0.4Ni0.6SmyFe2−yO4, where 0.0≤y≤0.1 were prepared by double sintering ceramic technique. The structure was characterized by X-ray diffraction, which has confirmed the formation of single-phase spinel structure. The samarium concentration dependence of lattice parameters obeys Vegard's law. The octahedral site radii increased with Sm content while the tetrahedral site radii decreased. Deviation from the ideal crystal structure (Δ) is found to decrease with Sm substitution, and the hopping length on the octahedral site is found to increase with Sm content. Hall measurement confirmed p-type conductivity behavior for Sm-doped ferrite and the main charge transport mechanism is hopping of halls between Ni2+ and Ni3+. Sintering at 1300°C resulted in low resistivity ferrite, which was found to increase with Sm content. Resistivity is governed by both charge carrier mobility and carrier concentration. It decreases with frequency, and this behavior with frequency is discussed according to Koop's theorem. The dielectric constant is found to decrease more rapidly at low frequencies than at higher frequencies while the dielectric constant increases with Sm content. The decrease in ε″ with frequency agrees with Deby's type relaxation process. Maximum in ε″ is observed when the hopping frequency is equal to the external electric field frequency. The variation in tanδ with frequency shows a similar nature to that of ε″ with frequency. The magnetization under applied magnetic field for the samples exhibits a clear hysteretic behavior. The scanning electron microscope (SEM) studies showed that the domain walls may tend to be trapped (pinned) by non-magnetic inclusions, precipitates and voids. The saturation magnetization (MS) increases with the sintering temperature, while the coercivity (HCi) is found to decrease.

Low-temperature structural study of the [formula omitted] series

A discontinuity in the temperature dependence of the lattice parameters while preserving the crystal symmetry was observed for TbPdAl, TbNiAl and TbPd 0.9 Ni 0.1 Al . We associate this result with the previously reported step-like change in the concentration dependence of lattice parameters in RE ( Ni 1 - x Cu x ) Al pseudo-ternary compounds. Our results corroborate the scenario for the RTX compounds with the ZrNiAl-type structure based on existence of a narrow interval of forbidden c / a values. For TbPdAl, TbNiAl and TbPd 0.9 Ni 0.1 Al we observed also a certain temperature interval of coexistence of two ZrNiAl-type phases characterized by two distinctly different c / a values.

Development of magnetic order in the pseudo-ternary series ErNi1−xCuxAl

The ErNi1−xCuxAl compounds have been studied from the view of crystallographic structure and magnetic properties by means of X-ray and neutron diffraction, magnetization and heat capacity measurements. The hexagonal ZrNiAl-type crystal structure adopted by the parent compounds ErNiAl and ErCuAl is conserved over the entire composition range. The concentration dependence of lattice parameters shows a discontinuity between x=0.5 and 0.6 both in paramagnetic and magnetically ordered phase. The evolution of magnetism from antiferromagnetism (AF) with Er-moments within the basal plane in ErNiAl to the simple ferromagnetism (F) with moments along the c-axis in ErCuAl is rather complex. The AF ordering is characterized by a propagation vector (12,0,12) with moments within the basal plane in the low Cu-concentration region for x up to 0.40. An incommensurate component with Er-moments along c develops within the range of 0.20⩽x⩽0.40 and grows on account of the commensurate one. The ErNi0.5Cu0.5Al is a simple F with moments along c. For concentrations with x=0.6 and 0.8 signs of short-range ordering were revealed.

Microstructure of Al 3Sc with ternary transition-metal additions

The microstructure of binary Al 3Sc and ternary Al 3(Sc 1− y X y ), where X is one of the transition metals from Group IIIA (Y), IVA (Ti, Zr or Hf) or VA (V, Nb or Ta), was investigated as a function of alloying element concentration for 0.1≤ y≤0.75. Alloys with Group IIIA and IVA additions exhibited a single L1 2 solid-solution phase with some Kirkendall porosity. At the highest concentration studied, a second phase precipitated with the D0 19 (Y), D0 22 (Ti) or D0 23 (Zr and Hf) structure. Conversely, alloys with Group VA additions exhibited both the L1 2 trialuminide phase and a dendritic trialuminide second phase with D0 22 structure for all concentrations studied. The solubility limit in the ternary L1 2-type Al 3(Sc 1− y X y ) phase was high for Group IIIA and IVA metals (almost 12.5 at.% or y=0.5), and much lower for Group VA metals (from about 1.8 at.% or y=0.07 for Ta to about 2.7 at.% or y=0.11 for V). Similarly, the solubility limit of Sc in the non-L1 2 phases decreases from the Group IIIA trialuminide to the Group VA trialuminides. The lattice parameter of the L1 2 solid-solution decreased linearly with increasing concentration of Group IVA and VA metals, but increased linearly with concentration of Y (Group IIIA). This linear concentration dependence of the lattice parameter is found to correlate with the atomic size mismatch between Sc and the transition metal. The microhardness of the L1 2 solid-solution increased linearly with increasing concentration of ternary elements. The concentration dependence of hardness is strongest for Group VA metals and weakest for Group IVA metals, for which a correlation is found with the concentration dependence of lattice parameter.

Powder diffraction refinement of theCo2Al5structure

The structure ofCo2Al5(hP28,P63/mmc) was refined by means of Rietveld method. The shortest Co–Al distance amounts 2.338 Å.Co2Al5shows a homogeneity range betweenCo29Al71andCo27.5Al72.5at 1125 K. The concentration dependence of lattice parameters was also measured. The axial ratioc/aincreases with increasing mole fraction of aluminum.

Magnetic properties of the UCoAl 1− xGa x intermetallic system

Results of structure and magnetization study of solid solutions UCoAl 1− x Ga x are presented. The ZrNiAl-type structure of parent compounds persists over whole series and a rather weak concentration dependence of lattice parameters is observed. UCoAl is a paramagnet showing metamagnetism above 1 T at low temperatures. Substitution of Ga for Al leads to gradual evolution of spontaneous magnetic moment, which amounts to 0.63 μ B in UCoGa. This behaviour associated with the 5f moment formation and ordering is discussed in terms of varying U–U exchange interactions mediated by the anisotropic 5f ligand hybridization.

Ferromagnetism in the UCo1-xRuxAl quasiternary intermetallics

Abstract We report the structure and magnetic investigations of the quasiternary UCo1-xRuxAl compounds crystallizing in the hexagonal structure of the ZrNiAl type. A large deviation from linearity is observed in the concentration dependence of lattice parameters, positive for a and negative for c, whereas the unit-cell volume V obeys Vegard's law satisfactorily. The nonlinearity is explained by a preferential occupation by the Co and Ru atoms of the two non-equivalent positions of the transition metal in the lattice. Although UCoAl and URuAl are paramagnetic down to low temperatures, ferromagnetism is observed in a wide concentration range of quasiternary solid solutions UCo1-xRuxAl. Both the Curie temperature and the spontaneous magnetization reach their maximum values of 60 K and 0.6μB (formula unit)−1 respectively in UCo0.7Ru0.3Al. The samples in the Ru concentration range 0.5 ≤ x ≤ 0.7 exhibit a second phase transition in the ordered state, indicated by anomalies in temperature dependence of both the ...

Magnetic properties of UCo1−xRuxSn solid solutions

UCo1−xRuxSn compounds crystallize in the layered hexagonal ZrNiAl-type structure with two inequivalent transition-metal sites T1 and T2 in T1-U and T2-Sn basal-plane layers. The concentration dependence of lattice parameters indicates a preferential occupation of the T2 sites by Ru atoms. Magnetic characteristics are changing substantially for x > 0.6, where the Ru atoms enter the T1 sites.