Optical Absorption Spectra Of VO2 Research Articles

Structural and spectroscopic properties of V2O5 doped zinc bismuth sodium borate glasses

Zinc bismuth sodium borate glasses with chemical composition (50-x)Bi2O3-30B2O3-(x-0.5)ZnO-20Na2CO3-(0.5)V2O5 [where x = 10, 15, 20, 25] were prepared by melt quenching technique. The prepared samples were studied by means of XRD, EPR, optical absorption and FTIR techniques. The amorphous nature was confirmed by the X-ray diffraction studies. The spin-Hamiltonian parameters (g & A) values, number of spins and paramagnetic susceptibility values have been calculated. The spin-Hamiltonian parameters indicate that the present glass samples are in octahedral sites with tetragonal distortion. The optical absorption spectra of VO2+ ions in the present glass system show single absorption band at ≈ 628 nm. The optical bandgap energies (Eopt) and Urbach energies (ΔE) have been calculated from the ultraviolet edges. The FTIR spectra reveal the BO, BO3, ZO, and BO4 bands in the present glass system.

Optical, physical and structural studies of vanadium doped P2O5–BaO–Li2O glasses

Glasses in the compositions (Li2O)25–(BaO)25–(P2O5)50−x–(V2O5)x (with x=0.5,1.0,1.5,2.0,2.5, and 3.0mol%) have been prepared by the conventional melt quenching technique. X-ray powder diffractrogram show broad peaks which conforms glassy nature of the sample. Differential scanning calorimetry (DSC) thermograms show characteristic glass transition temperature (Tg) and it increases with increasing substitution of V2O5 for P2O5. The measured physical parameters like density, refractive index, ionic concentration and electronic polarizability are found to vary linearly with increasing x. Infrared spectra exhibits few bands, which are attributed to (P=O)AS, (P=O)S, (V=O), (P–O–P)AS,P–O–V, (P–O–P)AS and O–P–O vibrations. The optical absorption spectra of VO2+ ions in these glasses show three bands and are assigned to the 2B2→ 2E,2B2→ 2B1 and 2B2→ 2A1 transitions. Electron paramagnetic resonance spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of Spin-Hamiltonian parameters indicate that the VO2+ ions are present in octahedral sites with tetragonal compression and belong to C4V symmetry.

EPR and Optical Absorption Study of VO2+ Ions Doped Potassium Hexaaquazinc (II) Sulfate Single Crystals

X-band single-crystal electron paramagnetic resonance (EPR) studies are done on VO2+ ions doped in potassium hexaaquazinc (II) sulfate, K2[Zn (H2O)6] (SO4)2 (PHZS) at room temperature. The spin Hamiltonian parameters, i.e., g and A tensors and their direction cosines, are evaluated by the standard diagonalization procedure using angular variation of the EPR spectra in three planes (ab, bc* and c*a), with the help of a computer program. The EPR spectrum is simulated using the EasySpin program to verify the calculations. The detailed EPR analysis indicates the presence of two magnetically inequivalent VO2+ sites. Both the vanadyl complexes are found to take up the substitutional position in the host lattice. The optical absorption spectrum of VO2+ ions doped in PHZS single crystal at room temperature is also recorded and four main d–d transfer bands in the visible region are assigned. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. With the help of assigned bands the crystal-field parameters (Dq, Ds and Dt) are evaluated. Finally, with the optical and EPR data, the nature of bonding in the complex is discussed.

Electron paramagnetic resonance and optical absorption study of VO2+-doped sodium zinc sulfate tetrahydrate single crystals

Single-crystal electron paramagnetic resonance (EPR) studies of VO2+ doped in sodium zinc sulfate tetrahydrate (Na2Zn(SO4)2·4H2O) have been carried out at room temperature. The results show the presence of three magnetically inequivalent VO2+ sites with different populations. The VO2+ impurity ions take up substitutional positions in the host lattice replacing Zn2+ ions. The angular variation of EPR spectra in three mutually orthogonal planes, bc, a*c and ba*, are used to determine the spin-Hamiltonian parameters. The optical absorption spectrum of VO2+ ions doped in the crystal lattice is also recorded at room temperature in the wavelength range 325–1100 nm. This is utilized to study the energy level structure of the VO2+ ion. By correlating the EPR and optical data, various molecular orbital coefficients of the VO2+ ion with its ligands are evaluated and the nature of bonding in the crystal is discussed.

EPR and UV studies of VO2+ ions in potassium d-gluconate monohydrate single crystals

Abstract Electron paramagnetic resonance (EPR) of VO2+ doped potassium hydrogen d -gluconate single crystals and powder have been examined at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes namely ac, ba and ca indicate two different VO2+ complexes. Each complex is located in different chemical environments, each environment containing two magnetically inequivalent VO2+ sites in distinct orientations occupying substitutional positions in the lattice and showing a very large angular dependence. The powder spectrum also clearly indicates four different VO2+ complexes, confirming the single crystal analysis. Crystalline field around the VO2+ ion is nearly axial. The optical absorption spectrum of VO2+ ions in the crystal lattice is also studied at room temperature. The characteristic spectrum of the VO2+ ions has two absorption bonds. The bond positions are at 17 857 and 11 235 cm–1. Spin Hamiltonian parameters and molecular orbital coefficients are calculated from the EPR and the optical data, and results are discussed.

ESR and optical absorption spectra of vanadyl ion in magnesium maleate dihydrate single crystals

Abstract ESR and optical absorption spectra of VO2+] ions doped in single crystals of magnesium maleate dihydrate have been studied between 300 K to 120 K. The spin-Hamiltonian parameters are determined from single crystal ESR data and also from powder ESR data. The g and A tensors are found to be axially symmetric. Two distinct vanadyl complexes at substitutional sites (Mg2+]) have been identified. From the optical and ESR data the molecular orbital bonding coefficients have been evaluated.

Electronic Spectra of VO2+ and Cu2+ Ions in Rubidium Zinc Sulphate Hexahydrate

Optical absorption spectra of VO2+ and Cu2+ ions in rubidium Zinc sulphate hexahydrate single crystals are investigated both at the laboratory and liquid nitrogen temperatures. The optical absorption spectrum of VO2+ is characteristic of tetragonal symmetry, whereas that of the Cu2+ is characteristic of rhombic symmetry. EPR spectra of polycrystalline samples of these substances are also recorded and analysed. By correlating the optical absorption and EPR studies, molecular orbital coefficients and orbital reduction parameters are calculated.

Studies on Optical Absorption Spectra of VO<sup>2+</sup> Ions in PbO-B<sub>2</sub>O<sub>3</sub> and R<sub>2</sub>O-PbO-B<sub>2</sub>O<sub>3</sub> (R=K or Na) Glasses and Bonding Mode of Pb Atoms in these Glasses

The optical absorption spectra of VO2+ ions dissolved in PbO-B2O3 and R2O-PbO-B2O3 glasses (R=K or Na) have been measured. By using the spectral results, the bonding mode of Pb in the glasses has been discussed. Judging from the dependence of peak position for B2*-Eπ* transition on the glass composition, it is suggested that although Pb behaves as a network modifier in the glasses, a part of Pb contributes to the formation of glass network. This relation is discussed on the basis of the relation between the peak wave number and ratio of four-coordinated B atoms to the total B atoms (N4B). On the assumption that the Pb ratio used in the formation of the glass network is α(x-0.2) in xPb(1-x)B2O3 glasses and (x+y-0.2) in xR2OyPbO(1-x-y)B2O3 glasses, the value of α is calculated to be 2.04.