Study of alkali borate glass containing tin by the Mössbauer effect

A number of alkali borate glasses containing tin oxide of base composition (100?X) % B₂O₃ + X % Me₂O + Y SnO₂ where Me = Li, Na or K, X = 10, 20 or 30 and Y is the quantity of SnO₂ introduced, were prepared and studied by the Mössbauer effect. It was shown that the value of the isomer shift increases while the value of the quadrupole splitting decreases with increasing ionic radius of the alkali ion. The value of the isomer shift and quadrupole splitting decrease with increasing alkali content. The observed asymmetry in the absorption lines was attributed to the Goldanskii effect. An explanation is suggested for the dependence of the ratio of the various valence and coordination structural states of the tin in the glass on the amount and nature of the alkali ions.     

Mössbauer study of nanocrystalline Co60Fe30Ni10 and Co50Fe35Ni15 alloys obtained during mechanical synthesis

The mechanical alloying method was used to prepare Co₆₀Fe₃₀Ni₁₀ and Co₅₀Fe₃₅Ni₁₅ alloys from the elemental powders. As X-ray diffraction studies proved the final products of milling were the solid solutions with b.c.c. lattice and the average grain size of about 60 nm. After heating of the alloys up to 993 K, the mixtures of two solid solutions with a b.c.c. and f.c.c. lattices were formed. Annealing of the alloys at 1173 K for 1 h resulted in the formation of solid solutions with an f.c.c. lattice. Mössbauer spectroscopy revealed hyperfine magnetic field distributions which reflected the different surroundings of ⁵⁷Fe isotopes by Co, Fe and Ni atoms, depending on the chemical composition of the alloy. The most probable atomic configurations were determined on the basis of a local environment model. The results of the macroscopic magnetic measurements testified that Co₆₀Fe₃₀Ni₁₀ and Co₅₀Fe₃₅Ni₁₅ alloys exhibited relatively good soft magnetic properties.     

Erratum to:Mössbauer Study of Iron Carbides Formed by Thermal Vacuum Deposition

Crystallography Reports - An Erratum to this paper has been published: https://doi.org/10.1134/S1063774521230012     

Evaluation of chemical durability,thermal properties and structure characteristics of Nb–Sr-phosphate glasses by Raman and NMR spectroscopy

Thermal properties, water durability and structure of Nb₂O₅–SrO–P₂O₅ glasses containing 0–25 mol% Nb₂O₅ and 35–60 mol% SrO were explored aiming to develop high refractive index optical glasses. Structure studied using Raman and NMR spectra reveals that by increasing Nb₂O₅ content, niobium plays the role as intermediate. Nb⁵⁺ tends to break P–O–P and O–P–O bonds forming [NbO₆] structure. Thus fractions of Q³ and Q² decrease, while Q¹ fraction increases. Furthermore the Q⁰ fraction replaces the lessened Q³ fraction. As P₂O₅ content is reduced to 30 mol%, partial [NbO₆]_octa turns into [NbO₄]_tetra and partial (Nb–O)_short-octa becomes (Nb–O)_short-tetra bond to stabilize the glass structure. Glass-transition and softening-temperatures of the glasses increase by increasing SrO and Nb₂O₅ contents. Thermal expansion coefficient increases by increasing SrO while decreases with Nb₂O₅ content. Water durability is enhanced as increasing Nb₂O₅ and SrO contents. Properties of the glasses correlate well with the worked out structure.     

Structure of the Fe–Co Nanowires Obtained by Template Synthesis

Crystallography Reports - Nanowires (NWs) from Fe–Co alloys with component ratios Fe : Co = 15 : 85, 52 : 48, and 65 : 35 are...     

Synthesis, X-ray and neutron diffraction and Mössbauer studies of SrFeOx crystals

Tetragonal single crystals of the nonstoichiometric strontium ferrate with the lattice parameters a = 3.8525(3) and c = 3.8781 (3) Å have been synthesized for the first time by the method of floating-zone melting in the SrFeO_x system. The neutron diffraction patterns of the crystals showed weak additional reflections indicating the formation of the superstructure with double spacing along the [hh0] direction. The Mössbauer spectra of the crystals were obtained and measured in the temperature range 80–300 K. It was established that below the temperature T _N = 232(1) K, the crystals are in the magnetically ordered state with 3/5 of iron ions being in the trivalent state and all the remaining iron ions in the tetravalent state. This leads to the crystal composition SrFeO_2.71. The electric resistivity of the crystals equal to 100 ω cm at room temperature drastically decreases at temperatures exceeding 470 K.     

Transition from amorphous semiconductor to amorphous insulator in hydrogenated carbon–germanium films investigated by IR spectroscopy

Thin a-Ge_XC_1?X:H plasma polymerized films, depending on deposition conditions, can be produced in two very different structures, namely amorphous semiconductor and amorphous insulator. The transition from amorphous insulator to amorphous semiconductor is related to the formation of germanium nanoclusters due to ions bombarding the surface of the growing material. This paper concentrates on investigations of the transition by means of IR spectroscopy. To this end a quantitative analysis of IR spectra obtained for thin films deposited on silicon substrate has been described and used for estimation of hydrogen atom concentration and bonding in the investigated material. It was found that the probability that a given H atom is bonded to a germanium or to a carbon atom is almost the same. This conclusion is true both for a-S and a-I films. The average concentration of hydrogen in the investigated material was found to be about 2.4–3.4 × 10²² cm^?2 which means that there are two times more atoms of the carbon family than hydrogen atoms in the film structure.     

Collective diffusion in the presence of substrate inhomogeneities and particle–particle interactions

A novel variational analytic approach to collective diffusion allowing the density dependent collective diffusion coefficient to be calculated in systems of interacting particles adsorbed on a crystalline substrate is presented. The approach, based on a kinetic lattice gas model extracts the diffusion coefficient directly from the master equations which account for the microscopic kinetics of the system in which microscopic processes underlying the diffusion are particle jumps between neighboring adsorption sites. Variational parameters minimizing the evaluated diffusional eigenvalue of the microscopic rate matrix are ‘geometrical’ and ‘correlational’ phases accounting, for the local potential energy landscape experienced by the adsorbed particle and the local correlations, respectively, i.e. an instantaneous occupation pattern of adsorption sites around the particle. Selected results, collective diffusion as a function of particle coverage, for the system of interacting particles adsorbed on a one dimensional non-homogeneous substrate with steps and for a system of non-interacting particles adsorbed on a two dimensional striped–stepped surface are presented and discussed. It is demonstrated in the latter case that the mean field approach which is known in the literature overestimates the diffusion coefficient and corresponds to the variational result in the limit of infinitely fast hopping kinetics in the direction parallel to steps.     

Magnetic Susceptibility of Deintercalated Tunnel Compound of KxCr5Se8 and Mössbauer Spectra of Kx(Cr0.95 57Fe0.05)5Se8

Abstract

KCr₅Se₈ has a TIV₅S₈-type structure, containing K ions in one-dimensional tunnels. Deintercalated samples of K_xCr₅Se₈ (0.32 ≤ x ≤ 0.93) were prepared by leaching method using Alc₃/FeCl₃ aqueous solution. These samples showed a broad peak of magnetic susceptibility at ca. 130 K. ⁵⁷Fe-Mössbauer spectra of K_x(Cr_0.95 ⁵⁷Fe_0.05)₅Se₈ (x = 1.0, 0.49) showed a quadrupole doublet at 300 K. Magnetic sextets appeared at 4.2 K in both samples, indicative of magnetic ordering. The observed isomer shift indicated that the charge of Fe is +3 in both samples. It was proposed that Se^2- was partially oxidized by the deintercalation.     

Study of the alkaline environment in mixed alkali compositions by multiple-quantum magic angle nuclear magnetic resonance (MQ–MAS NMR)

45S5 Bioglasses of the composition 46.1 SiO₂–2.6 P₂O₅–26.9 CaO–(24.4 ? x) Na₂O–xMe₂O (Me = Li or K) have been investigated using MAS NMR and MQ–MAS NMR methods. The analysis of the ²⁹Si MAS NMR spectrum revealed two lineshapes whose chemical shift is consistent with two silica Q_n=2,3 species. The ³¹P MAS NMR spectrum reveals the effect of both Na and Ca ions. The chemical shift of the observed ³¹P signal is intermediate between those of Na₃PO₄ (near 10 ppm) and Ca₃(PO₄)₂ (near 3–0 ppm) species. The ²³Na MAS NMR spectra were observed in the alkali oxide composition: 24.4 Na₂O, 12.2 Na₂O–12.2 K₂O and 12.2 Na₂O–12.2 Li₂O. The substitution of Na with Li or K was done to determine the extend of alteration of the glass structure. This goal was best accomplished by ²³Na MQ–MAS NMR. The two-dimensional spectra revealed three sites in the 24.4 mol% Na₂O glass. These sites were not resolved in the 1D MAS NMR spectroscopy. In the mixed glasses, only two sites were obtained.     

Mössbauer and Magnetic Study of Lanthanum Manganite La1 – xCaxMn0.98Fe0.02O3 + δ (x = 0.05, 0.10, 0.20): Nonstoichiometric and Stoichiometric Composition

Crystallography Reports - Mössbauer and magnetic study of calcium-doped lanthanum manganites La1 – xCaxMn0.98Fe0.02O3 + δ (x = 0.05, 0.10, 0.20)...     

Synthesis,infrared and Mössbauer characterization and X-ray crystal structure of 1,10-phenanthrolinium tetrachloromethoxy phenylantimonate(V)

The compound has been characterized by X-ray crystal structure determination, Mössbauer and i.r. spectroscopy. It crystallizes in the monoclinic space groupP2 ₁ /c (No. 14) witha=24.228(4),b=8.335(2),c=23.975(4) Å,=117.83(3)° andZ=8. Least-squares refinement on 3749 observed reflections gave finalR=0.034 (R _w=0.037). The compound is constituted by [(C₆H₅)SbCl₄OMe]^– anions andphenH⁺cations. The coordination polyhedron about Sb is an octahedron (Sb-Cl 2.416(3), Sb-O 1.962(7) and Sb-C 2.138(9) Å). The whole structure is characterized by two short contacts (O(1)N(2) 2.76(1) O(2)N(4) 2.75(1) Å) involving the methoxy oxygens of the two independent anionic units [(C₆H₅)SbCl₄OMe]^– and two nitrogens of the two independent phenanthrolinium moieties.     

Free volume and viscosity of Fe–Co–Cr–Mo–C–B–Y bulk metallic glasses and their correlation with glass-forming ability

In this work, the variation of the glass-forming ability (GFA) in Fe–Co–Cr–Mo–C–B–Y alloy system with Co addition has been investigated from the viewpoints of non-isothermal viscosity and free volume. The best GFA for the alloy containing 7% Co is found to closely relate with its highest viscosity, and the minimum sizes and lowest concentrations of the intermediate and largest open volumes. The results may provide more insights into the formation mechanism of metallic glasses.     

Electrochromic properties of nickel oxide and mixed Co/Ni oxide films prepared via sol–gel route

The Ni oxide and mixed Co/Ni oxide films were prepared by sol–gel dip coating method at optimum conditions. The XRD analysis reveals the pure and Co mixed nickel oxide films to be in amorphous state. The field emission SEM images reveal nanopore like structure for Ni oxide film and well defined grains with pores for Ni oxide films containing 5 wt.% of Co. Electrochromic properties have been studied using cyclic voltammetric (CV) and in situ spectro-electrochemical techniques. The pure and cobalt mixed (5 wt.%) Ni oxide films exhibit anodic/cathodic diffusion coefficient of 4.93 ± 0.14/3.74 ± 0.10 × 10^?10 cm²/s and 10.00 ± 0.24/7.60 ± 0.20 × 10^?10 cm²/s respectively after 300 cycles. The cobalt mixed (5 wt.%) Ni oxide films exhibit the bleached/coloured state transmission of 90.42/7.21% with a photopic constrast ratio of 12.54 and the colouration and bleaching time were 5.9 and 2.4 s respectively. The addition of cobalt beyond 5% leads to poor transparency and inhibited electrochromic switching character.