Tetragonal Compression Research Articles

Spectral analysis and characterization of Na2O-SiO2-ZrO2 glasses doped with V2O5

Na2O-SiO2-ZrO2 glasses doped with V2O5 were prepared with the melt quenching method, and were then analyzed using various techniques; in particular, with X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and optical absorption, photoluminescence, electron spin resonance (ESR), and Fourier transform infrared (FT-IR) transmission spectroscopy. The obtained results indicate that, in the studied glasses, vanadyl complexes tend to undergo a reduction from V5+ ions to V4+ ions. XRD and EDS data suggest that the glasses have amorphous nature with randomly distributed grains within the glass matrix. The optical absorption spectra show two transitions: 2B2g→2B1g and 2B2g→2Eg. The photoluminescence spectra exhibit a broad band from 750-900 nm, indicating the 2E→2T2 transition of vanadyl ions. The energies of the band gaps decreased gradually with increasing V2O5 content. The ESR spectra suggest that V4+ ions are situated in octahedral sites with tetragonal compression. The FT-IR spectra confirm the presence of various structural units within the glasses. Finally, the dielectric properties of the glasses were also measured, showing that the dielectric constant (ε′) and the loss tangent (tan δ) increase as the content of vanadium ions increases, indicating presence of V4+ ions within the glass matrix.

Synthesis and investigation of the V2O5 effect on the properties of Na2O–NiO-(1-x)P2O5–xV2O5 (0≤x≤0.6) system

This study reports on the properties of glasses and glass-ceramics isolated in a novel ternary system Na2O–NiO-(1-x)P2O5–xV2O5 with varying concentrations of V2O5 (x = 0, 0.2, 0.4, and 0.6 mol%). The materials were prepared by melting the mixture of reagents with stoichiometric proportions. Their amorphous and crystalline nature was confirmed via the XRD analysis. The vitreous feature and thermal parameters of the glasses were explored using differential scanning calorimetry. The density values have shown an increase and a slight decrease in the molar volume with the increase in the V2O5 content. The elemental composition of the glass and glass-ceramics was studied using energy-dispersive X-ray spectroscopy. In addition, the study examined the influence of the composition on the structure of the materials using both IR and Raman spectroscopies. XRD analysis of annealed samples revealed the presence of different crystalline phases depending on the V2O5 content. The EPR results were influenced by the variation of concentration of V2O5 and indicated the presence of V4+ ions in octahedral sites with tetragonal compression. The analysis of the magnetization according to the magnetic field at different temperatures showed a ferromagnetic behavior at low temperatures and a paramagnetic one at higher temperatures for all glasses. Magnetic susceptibility data reveal a Curie-Weiss behavior and the predominance of antiferromagnetic interactions. The dielectric studies were conducted as a function of temperature and frequencies to evaluate the composition effect on the dielectric constant, dielectric loss, and ionic conductivity. Electrical features were also examined using impedance spectroscopy.

Electron Spin Resonance of V4+ Ions in K2O-B2O3-V2O5 Glasses

In the present work the ESR study of potassium borovanadate (K2O-B2O3-V2O5) glasses is reported at room temperature and liquid nitrogen temperature. The spectra at liquid nitrogen temperature is similar to at room temperature except the indusial hyperfine lines are sharper and more intense which might be ascribed to a spin-lattice relaxation effect. The ESR parameters were calculated at room temperature and shows that in-plane π bonding is somewhat covalent and covalency is nearly independent of concentration of K2O. The octahedral site with a tetragonal compression gives g value in the order g׀׀< g< ge(=2.0023). It is observed that the V4+ ions in the present sample exist as VO2+ ions in octahedral coordination with a tetragonal compression and belong to C4v symmetry.

Effect of VO2+ ions incorporation on paramagnetic behavior of Calcium Borophosphate (CaBP) nanophosphors: A detailed study of structural and EPR properties

Novel phosphor luminous materials have attracted much interest due to their prevalent use in light emitting diodes (LEDs), Field-emission display (FED), Plasma display panel (PDP), and fluorescent markers in biomedicine. Vanadium steel is utilised for crankshafts, bicycle frames, gears, and other things. Solid-state technique is used to produce samples of Calcium Borophosphate (CaBP) Nanophosphors that incorporate VO2+ ions. At various VO2+ concentrations, the structural and EPR features have been investigated. The powder XRD patterns and predicted lattice cell properties allow us to determine that the generated phosphors belong to the triclinic crystal system. Crystallite sizes for VO2+ doped CaBP nanophosphors are typically in the range of 29 nm. The octahedral coordination of VO2+ with tetragonal compression is shown in the EPR data. An increase in the bonding parameters is observed with an icnrease in VO2+ concentration. The Tetragonal and Spin Hamiltonian values and the calculated crystal field support the same.

Theoretical analysis of resonant inelastic x-ray scattering spectra of Ca2RuO4

We calculate the resonant inelastic x-ray scattering (RIXS) spectra of a $4d$-electron Mott insulator ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{4}$ that exhibits spin-orbit entangled magnetic ordering. Considering the Ru ${L}_{3}$-edge RIXS, we identify four different types of excitations: magnetic dipolar transitions, quadrupolar transitions changing total angular momentum by $\mathrm{\ensuremath{\Delta}}J=2$, spin-state transitions with $\mathrm{\ensuremath{\Delta}}S=1$, and ${t}_{2g}\ensuremath{\rightarrow}{e}_{g}$ orbital transitions across the crystal-field and Hund's coupling derived levels. We provide analytical expressions for the magnetic transitions and the $\mathrm{\ensuremath{\Delta}}J\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}2$ transitions in the tetragonal compression limit, which are generally applicable to other compounds with ${t}_{2g}^{4}$ configurations in a square lattice. Intriguingly, we find that upon tetragonal compression the dipole-forbidden $\mathrm{\ensuremath{\Delta}}J=2$ transitions acquire large spectral weights with pronounced polarization dependencies, which are consistent with the experimental observations. Our numerical simulations show that this is due to a constructive interference between dipolar and quadrupolar scattering channels.

Visible light driven robust photocatalytic activity in vanadium-doped ZnO/SnS core-shell nanocomposites for decolorization of MB dye towards wastewater treatment

Vanadium metal oxide (V2O5) doped ZnO/SnS core-shell nanocomposites are fabricated by hydrothermal method at 2200C for 10 hours. All synthesized Nanocomposites were optically, structurally, morphologically and magnetically examined by different techniques such as UV-DRS, XRD, TEM, electron paramagnetic resonance (EPR), XPS and PL techniques. The photocatalytic activity (PCA) was studied for methylene blue (MB) model pollutant dye under 300 W visible light illumination. XRD peaks confirmed the mixed phase abundance with hexagonal ZnO and orthorhombic SnS. TEM micrographs inferred uneven surface with more agglomeration. XPS conclude V4+ oxidation state for vanadyl atoms along with constitutes elements. The UV-DRS inferred red shift in bandgap. EPR argued that vanadyl ions perform tetragonal compression distorted octahedral site symmetry. PL study described quantum confinement effect. The achieved MB dye degradation under visible light illumination is more than 96% in 2 hours. Enhanced PCA argued owing to plasmonic effect and tunable energy bandgap nature of heterogeneous semiconducting materials.

Theoretical investigations on the defect structures and g factors for V4+ in 30PbO-5Bi2 O3 -(65-x)SiO2 glasses at different concentrations.

For 3d1 (V4+ ) impurity in 30PbO-5Bi2 O3 -(65-x)SiO2 glass systems with different concentrations x of V2O5, the defect structures and gyromagnetic factors are theoretically investigated by using the perturbation formulas of g factors for a tetragonally compressed octahedral 3d1 group. The concentration dependences of d-d transition band and g factors are suitably explained from the Fourier type concentration functions of the cubic crystal field parameter Dq, covalency factor N and relative tetragonal compression ratio ρ. The above concentration dependences of these quantities are suitably illustrated by the modifications of the local crystal field strength and electron cloud distribution with increasing x. The concentration variations of the electrical conductivity and dielectric relaxation are further analyzed from the stability of the systems in view of two competitive factors (increasing network polymerization and bulk stability at low concentrations and decreasing former SiO2 and stability at high concentrations).

A comparable study of the optical spectra and EPR parameters for 3d1 - and 3d9 -doped MgNH4 PO4 ·6H2 O.

VO2+ (3d1 ) and Cu2+ (3d9 ) are the two complementary states that usually show opposite distortions when they are doped in crystals. In this work, the optical absorption spectra (OAS), electron paramagnetic resonance (EPR) parameters, and local structure (LS) for VO2+ (and Cu2+ ) in MgNH4 PO4 ·6H2 O (MPPH) are uniformly investigated on the basis of the high-order perturbation formulas for a 3d1 (and 3d9 ) ion in tetragonally compressed (and elongated) octahedra, respectively. In the calculated formulas, the required crystal-field parameters can be obtained from the superposition model and reasonably linked with the LS distortion for VO2+ and Cu2+ centers. Based on the calculations, the tetragonal compressed [VO(H2 O)5 ]2+ cluster (and tetragonal elongated [Cu(H2 O)6 ]2+ cluster) is found to suffer tetragonal compression ratio of 1.65% and tetragonal elongation ratio of 3.8% along C4 -axis, respectively, due to the Jahn-Teller (JT) effect. The theoretical EPR parameters based on the above lattice distortions agree well with the experimental data, and the LS of the VO2+ and Cu2+ centers in MPPH is discussed.

Theoretical analysis on strontium-tellurium content dependencies of defect structures and spin Hamiltonian parameters for strontium-tellurium titanium borate glasses with V2O5 dopants

Based on the perturbation formulae of the spin Hamiltonian parameters (SHPs) for a tetragonally compressed octahedral 3d1 cluster, the defect structures and SHPs of V4+ in strontium-tellurium borate ((30-x)SrO-xTeO2-10TiO2-58B2O3-2V2O5 at distinct TeO2 contents x = 1, 2, 3, 4 and 5 mol %) glasses are systematically investigated. The involved model quantities (i.e. covalent factor N, tetragonal compression ratio τ, core polarization constant κ and reduction factor H) at various x reasonably reproduce the experimental SHPs, and these quantities are further fitted with uniform Fourier-type content functions (FTCF) with merely three adjusted parameters. The different content fluctuations of these quantities are ascribed to content declines of the strong network modifier SrO and hence the modulations in local tetragonal compression, system compactness and electron cloud distribution near vanadium in the glass network.

Theoretical studies on the g factors, optical absorption, and their concentration variations for Mo5+ in 40PbO-(10 - x)Y2 O3 -50P2 O5 :xMoO3 glass.

On the basis of the higher order perturbation formulas of g factors for a 4d1 group in tetragonally compressed octahedra, the g factors, optical absorption, local structure, and their concentration dependences of pentavalent molybdenum in 40PbO-(10 - x)Y2 O3 -50P2 O5 :xMoO3 (1 ≤ x ≤ 5mol%) glass are uniformly investigated. The experimental optical absorption spectra and g factors for Mo5+ at various concentrations x are reasonably regenerated by using the reasonable exponential concentration functions of the cubic field parameter Dq , covalent factor N, and relative tetragonal compression ratio ρ. The tetragonal compression ratio ρ due to the Jahn-Teller effect was found in the range of 3.8% to 4.2%. The decreasing trend of Dq and N and the increasing trend of ρ with concentration can be interpreted as the fact that the variations of MoO3 and Y2 O3 concentrations lead to the modulations of local structure and electron cloud distribution around Mo5+ , associated with the adjustment of the glass network. The concentration dependence of optical basicity is also analyzed for the above glass systems.

Theoretical studies of the concentration dependences of d-d transition band, g factors, and local distortion for V4+ in Li2 O-PbO-B2 O3 -P2 O5 glasses.

In this work, the g factors, d-d transition band, local distortion, and their concentration dependences for impurity V4+ in 20Li2 O-20PbO-45B2 O3 -(15 - x)P2 O5 :V2 O5 (0 ≤ x ≤ 2.5 mol%) glasses are theoretically investigated by using perturbation formulas of g factors for a tetragonally compressed octahedral 3d1 cluster. In the light of the cubic polynomial concentration functions for cubic field parameter Dq , covalency factor N, and relative tetragonal compression ratio ρ, the calculated concentration dependences of d-d transition band and g factors for V4+ show good agreement with the experimental data. With increasing x, N (≈0.7682-0.8165) displays the monotonously increasing trend, whereas ρ (≈6.5-4.2%) and Dq (≈1504.9-1481.1 cm-1 ) exhibit the decreasing tendencies. The above concentration dependences can be ascribed to the modifications of the V4+ -O2- bonding and orbital admixtures around the impurity V4+ due to the effects of V2 O5 doping on the stability of the glass network, the strength of local crystal fields, and the electron cloud distribution.

Physical, structural and optical characterization of silica-borotellurite glasses containing vanadium and nickel ions

Silica borotellurite glasses with compositions SiO2][SiO2][SiO2]0.2}0.99{V2O5}0.01]1-z (Ni0)z (where z = 0.005,0.010,0.015,0.020 and 0.025 M fraction) had been prepared by conventional melt quenching technique. X-Ray Diffractograms spectra confirm the amorphous nature of the prepared glasses. Study of infrared (IR) spectroscopy reveals an increase in the formation of nonbridging oxygens (NBOs) as nickel concentration increases. This resulted in the decrease of density and oxygen packing density (OPD) of the glass. The observed ESR spectra confirmed that V4+ ions exist as vanadyl ion in the octahedral coordination with tetragonal compression. Based on UV–vis absorption spectra, four absorption bands have been observed with indirect optical band gap, Urbach's energy, refractive index and other optical parameters have been calculated. The Ni2+ ions were distributed with octahedral and tetrahedral coordination of the ligand field. Nevertheless, the octahedral coordination of Ni2+ dominated over tetrahedral coordination with the increase of NiO concentration consequently, confirmed the increase in NBOs from the IR spectra. These observations reflect the decrease in optical band gap, metallization criterion and the increase in Urbach's energy and refractive index.

Theoretical studies on the concentration dependences of optical spectra and spin Hamiltonian parameters for V4+ in CdO–SrO–B2O3–SiO2 glasses

The optical absorption spectra, spin Hamiltonian parameters (SHPs, g factors and hyperfine structure constants) and their concentration dependences for impurity V4+ in 10CdO-(20-x)SrO–50B2O3–20SiO2–xV2O5 (x = 0.5, 1, 1.5, 2, 2.5 mol%) glasses are theoretically studied based on the perturbation formulas of these parameters for a tetragonally compressed octahedral 3 d1 cluster. The measured optical transition bands and SHPs for V4+ in CdO-(20-x)SrO–B2O3–SiO2–xV2O5 glasses at various V2O5 concentrations x can be suitably reproduced by using the reasonable cubic concentrations functions for the related model quantities (i.e., cubic field parameter Dq, covalency factor N, relative tetragonal compression ratio ρ, core polarization constant κ and reduction factor H). The impurity V4+ center is found to suffer the relative tetragonal compression ratio by about 4–6% of the Jahn-Teller nature. In view of possible applications of these glass systems in various fields such as optics, chemistry, medicine and industry, present studies would be helpful for the explorations of structures and properties for CdO–SrO–B2O3–SiO2 and similar glasses as well as the enhancement of the properties containing transition-metal dopants at distinct concentrations.

Vanadyl doped Li-zinc borate glasses: Optical and ESR study

Glasses with the composition xV2O5-(15-x) Li2O-70B2O3-15ZnO, for x varies from 0 to 4 mol. %, were synthesized using standard quenching technique. The amorphous nature for selected samples (x= 0, 1 and 4 mol. %) was ensured from X-ray diffraction (XRD) measurements. The samples were found to compose mainly from BO3 and BO4 basic structural units as inferred from Fourier transform infrared (FTIR) data. The number of BO4 (BO3) structural units was found to decrease (increase) with increasing the number of NBOs. These structural modifications within the glass network are responsible for the here observed composition dependence optical energy gap (Eotp) and Urbach band tail (ΔE). The electron spin resonance (ESR) results revealed a tetragonal compression for VO2+ ions present in octahedral coordination, with distinct optical transitions in the visible spectral regime.

Theoretical studies of the EPR spectra and local structures for Cu2+ and V4+ doped halo-borate glasses

Local structure and the effect of halide on MX∙M2O∙B2O3 (M = Pb, Ba; X = F, Cl, Br) glasses doped with Cu2+ and VO2+ are investigated by means of the perturbation calculations of the spin Hamiltonian parameters (SHPs). Based on the fitted EPR results, [CuO6]10− and [VO6]8− clusters prefer to suffer the tetragonal elongation and compression distortions, respectively. Compare the ionic radius of Cu2+ with V4+ and Pb2+ with Ba2+ in MX∙M2O∙B2O3, the glasses with larger ionic radius of metal may induce larger tetragonal distortions and larger g anisotropies. The d-d transition bands show whole opposite trends for 3d9 and 3d1 impurities with the similar fluctuations due to the increase of non-bridging oxygen. The d-d transition bands and g factorsare are also analyzed from the electronegativities of incorporated halides. The values of basicities Λth of BCBBV are found larger than PCPBC and PbX-PbO-B2O3 glasses due to stronger ionicity of Ba than Pb.

Investigations of defect structures for V4+ in CBPB glasses with distinct V2O5 contents

The defect structure, d-d transition and EPR parameters for V4+ in 10CaF2-(20-x)Bi2O3-60P2O5-10B2O3-xV2O5 (CBPB) glasses with distinct V2O5 contents x are theoretically investigated from the perturbation formulas for tetragonally compressed octahedral 3d1 clusters. Linearly decreasing cubic field parameter Dq or increasing g|| and g⊥ with x are suitably reproduced by linearly decreasing content function of Dq or decreasing and increasing content functions of covalence factor N and relative tetragonal compression ratio τ. The overall slightly increasing and decreasing average and anisotropy of hyperfine structure constants are illustrated as the cubic increasing content functions of core polarization constant κ and reduction factor H. These content dependences are ascribed to the modulations in local tetragonal compression, crystal-field strength and electron cloud distribution near V4+ with x. V2O5 as strong network modifier inducing depolymerization of phosphate long chains and Bi2O3 as network former and modifier exhibiting discontinuous changes with x may account for these modifications of the local structural properties.

Theoretical analysis on lead halides content dependences of defect structures and spin Hamiltonian parameters in lead halo borate glass composites with V2O5 dopants

The defect structures and spin Hamiltonian parameters (SHPs) for V4+ in lead halo borate (xPbX2–(30 − x)PbO–68B2O3, X = F, Cl, Br and x = 5, 10, 15, 20 and 25 mol%) glass composites containing 2 mol% of V2O5 dopant are theoretically studied by applying the perturbation formulas of the SHPs for tetragonally compressed octahedral 3d1 clusters. The experimental SHPs are suitably reproduced by the optimal covalency factor N, relative tetragonal compression ratio ρ, core polarization constant κ and reduction factor H at various x, which are simulated with the corresponding Fourier type content functions. The distinct deviations of these quantities from the relevant simulated Fourier type content functions at 5 mol% of PbCl2 and PbBr2 are reasonably explained from the modifications of compactness and electronic cloud redistributions around V4+ at this content. This is supported by the previous analysis on the content variations of ionic conductivity of the systems.

Magneto-Structural Relationship of Tetragonally-Compressed Octahedral Iron(II) Complex Surrounded by a pseudo-S6 Symmetric Hexakis-Dimethylsulfoxide Environment

Since the octahedral high-spin iron(II) complex has the 5T2g ground term, the spin-orbit coupling should be considered in magnetic analysis; however, such treatment is rarely seen in recent papers, although the symmetry-sensitive property is of interest to investigate in detail. A method to consider the T-term magnetism was well constructed more than half a century ago. On the other hand, the method has been still improved in recent years. In this study, the octahedral high-spin iron(II) complex [Fe(dmso)6][BPh4]2 (dmso: dimethylsulfoxide) was newly prepared, and the single-crystal X-ray diffraction method revealed the tetragonal compression of the D4-symmetric coordination geometry around the iron(II) ion and the pseudo-S6 hexakis-dmso environment. From the magnetic data, the sign of the axial splitting parameter, Δ, was found to be negative, indicating the 5E ground state in the D4 symmetry. The DFT computation showed the electronic configuration of (dxz)2(dx2−y2)1(dyz)1(dxy)1(dz2)1 due to the tetragonal compression and the pseudo-S6 environment of dmso π orbitals. The electronic configuration corresponded to the 5E ground term, which was in agreement with the negative Δ value. Therefore, the structurally predicted ground state was consistent with the estimation from the magnetic measurements.

Theoretical study of the local distortions and the EPR parameters for VO2+ and Cu2+ centers in oxyfluoroborate glasses

Theoretical calculations of the local structures and the electron paramagnetic resonance (EPR) parameters for the impurities VO2+ and Cu2+ centers in oxyfluoroborate glasses (OFG) were performed by using the perturbation formulas of the EPR parameters for tetragonally compressed octahedral [VO6]8- and tetragonally elongated octahedral [CuO6]10− clusters, respectively. In the calculations, the required crystal-field (CF) parameters are estimated from the superposition model which enables correlation of the CF parameters and hence the EPR parameters with the tetragonal distortion (characterized by the relative tetragonal elongation (or compression) ratio τ along the C4 axis) of [VO6]8- (or [CuO6]10−) cluster. Based on the calculations, the [VO6]8- and [CuO6]10− clusters are found to undergo the tetragonal compression (τ ≈ 1.7%) and elongation (τ ≈ 2.9%) along the C4 axis, the signs of A|| and A⊥ for VO2+ and Cu2+ centers in OFG were also determined. The above theoretical approach on local structural properties would enhance the understanding of the structural properties for other oxide glasses with transition-metal (TM) dopants.

Studies on the local structure and spin Hamiltonian parameters for V4+ in Na2 O-PbO-Bi2 O3 -SiO2 glass ceramics.

The local structure, d-d transition band, and spin Hamiltonian parameters (SHPs) are theoretically studied for the V4+ probe in Na2 O-PbO-Bi2 O3 -SiO2 (NPBS) glass ceramics containing V2 O5 dopant with various concentration x (0 ≤ x ≤ 5 mol%) by using the perturbation formulas of the SHPs for tetragonally compressed octahedral 3d1 clusters. The first decreasing (or increasing) and then increasing (or decreasing) d-d transition band (= 10 Dq ) and hyperfine structure constants A// and A⊥ (or g factors g// and g⊥ ) with x can be suitably simulated with the similarly varying Fourier type concentration functions of cubic field parameter Dq , covalence factor N, core polarization constant κ, and reduction factor H (or relative tetragonal compression ratio ρ), with the minima (or maxima) at the middle concentration x = 3 mol%, respectively. The above concentration variations of SHPs and the related quantities may originate from the modifications of local crystal field strength, tetragonal compression, and electron cloud distribution near the impurity V4+ with x, corresponding to the highest [V4+ ]/[V5+ ] ratio at 3 mol%. Present studies would be helpful to explore novel sodium lead bismuth silicate glass ceramics by modifying the concentration of V2 O5 dopant.