The correlation between the structural, optical, and electrical properties in mixed alkali fluoroborate glasses containing vanadium ions (original) (raw)
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Journal of Non-Crystalline Solids, 2015
New different series of xV 2 O 3 •(100 − x)[4PbO 2 ·Pb] glasses were prepared by melt-quenching method in a wide range of compositions defined by the parameter x = 0-30 mol% V 2 O 5 . InfraRed (IR) data reveal that by increasing the V 2 O 5 content, the glass network was transformed into a mixture of modified [VO 4 ] structural units, namely pyrovanadate and orthovanadate ones. The UltraViolet-Visible (UV-VIS) spectra show that addition of V 2 O 5 produces a gradual shift of the absorption edge towards the higher wavelength side (indicating the increase in concentration of vanadyl species) and a decrease of the gap energy. The shape of the Electron Spin Resonance (ESR) spectra changes with increasing the V 2 O 5 content suggesting that the interactions between vanadium centers strongly depend on x parameter which plays an important role. A hyperfine structure becomes visible in the glass with x = 20 mol% V 2 O 5 suggesting modifications of the glass structure caused by the network modifier. If the network is moderately disrupted the formation of Pb +2 -V +4 pairs was coupled through the oxygen atom or the interactions within V +4 -O-V +5 chains mask hyperfine structure. The shape of cyclic voltammograms, redox waves and good reversibility of the x = 20 mol% V 2 O 5 glassy electrode depends on the electrolyte acidity and electrochemically active species present in the glass network.
SYNTHESIS AND CHARACTERIZATION OF VANADYL ION DOPED ALKALINE HALIDE BORATE GLASSES
The Glasses have been prepared with a composition xBaCl 2 . (0.3-x) BaO. 0.68B 2 O 3 +0.02V 2 O 5 (x=0, 0.02, 0.05, 0.10) with the traditional melt-quenching technique. The glass preparation was confirmed with the help of XRD(X Ray Diffraction). The density measurements were performed with xylene as the immersion liquid and this data was used for the calculations of the molar volume. The study was further extended with some approach towards the calculation of the theoretical optical basicity so as to determine the oxygen covalency. , used in the preparation of the glasses were of Analar (AR) grade quality (with purity > 99%). The batch composition in mol% of glasses studied in the present work has been given in table 1. The chemicals were weighed accurately in an electronic balance (with
EPR, FTIR, thermal and electrical properties of VO2+ doped BaCl2BaOB2O3 glasses
Glasses with composition xBaCl2(30-x)BaO68B2O32V2O5 (x = 0, 2, 5, 10, in mol%) were prepared by the conventional melt quenching technique. The Electron paramagnetic resonance (EPR) spectra have been recorded at room temperature and the Spin Hamiltonian Parameters (SHPs) of VO2+ ion were calculated. It was observed that with the increase in BaCl2:BaO ratio, the tetragonal symmetry of the V4+O6 complex was improved and there was an expansion in the 3dxy orbital. Infrared (IR) transmission spectra were recorded at room temperature using FTIR spectroscope and it was found that in glass structure, BO3 triangular units are being replaced by the BO4 tetrahedral units on addition of halide content. The glass transition temperature (Tg) and crystalline temperature (Tx) were determined using Simultaneous Thermal Analyzer (STA). The trends in Tg and Tx suggests that there is a decrease in glass stability and glass forming ability (GFA) with increasing Cl ions content. The dc conductivity & impedance spectroscopy has been analyzed in the temperature region from 353 K to 573 K and in the frequency range from 10 Hz to 7 MHz. The frequency dependence of conductivity was found in accordance with the Jonscher’s relation.
Transparent and stable glasses in the chemical composition of Li2O–LiF–B2O3–MO (M = Zn and Cd) have been prepared by a conventional melt quenching method. For these glasses, absorption spectra, structural (XRD, FT-IR, and Raman spectra), thermal (TG–DTA and DSC), dielectric (ɛ′, ɛ″, tan δ), ac conductivity (σac), and electric modulus (M′ and M″) have been investigated. Amorphous nature of these glasses has been confirmed from their XRD profiles. The LFB glasses with the presence of ZnO or CdO an extended UV-transmission ability has been achieved. The measured FT-IR and Raman spectra have exhibited the vibrational bands of B–O from [BO3] and [BO4] units and Li–O. The dielectric properties (tan δ, dielectric constant (ɛ′), dielectric loss (ɛ″)), electrical modulus and electrical conductivity (σac) of these glasses have also been studied from 100 Hz to 1 MHz at the room temperature. Based on the trends noticed in the ac conductivities, the present glasses could be found useful as battery cathode materials.
Oxy-chloride bismuth-borate glasses with composition xMgCl2·(30 − x)MgO·20Bi2O3·50B2O3containing2 mol% doping of V2O5(x = 12, 15, 20, 25 and 30) are prepared by melt-quenching technique. The struc-tural, thermal and optical behaviors are explained by analyzing the data obtained from density (D), molarvolume (Vm), theoretical optical basicity (th), differential scanning calorimetry (DSC), FTIR and UV–visresults. A decrease in D and increase in Vm(except for sample MBV3 for which D is maximum) on increas-ing chloride content suggests the formation of non-bridging oxygen atoms. Maximum glass transitiontemperature (Tg) and crystallization temperature (Tx) have been observed for sample MBV3. The glassstability (S) and stability ratio (S/Tg) have been calculated from the values of Tgand Txand both are havingmaximum values for sample MBV3. Study of the FTIR spectra in the mid-IR range reveals the presence ofboth triangular and tetrahedral coordinated boron. The optical studies through UV–vis spectral analysisshow non-sharp edge. The optical band gap (Eg) is also maximum for sample MBV3.
Optical and thermal investigations on vanadyl doped zinc lithium borate glasses
tUsing standard melt-quench technique, transition metal oxide (2 mol% of V2O5) doped glasses havingcomposition xZnO·(30 − x)Li2O·70B2O3(x = 0, 2, 5, 7 and 10) are prepared. The density (D) is measuredusing buoyancy and found to be lying between 2.21 and 2.45 g/cm3with an increasing trend on substitut-ing ZnO contents in place of Li2O. The theoretical optical basicity (th) is calculated and found to increasewith increasing inclusion of ZnO indicating an increase in the ionic character. The molar refraction (Rm),refractive index (nr) and molar polarizability (˛m) are calculated and explained on the basis of structuralchanges. The optical absorption spectra have been used to evaluate the values of optical band gap (Eopt)and band tailing parameter (B). It is observed that Eoptdecreases with the increasing contents of ZnO inbase glass matrix. The decrease in Eoptis an evidence of enhancement in the number of non-bridgingoxygen atoms (NBOs) thereby increasing the four-coordinated boron atoms. The as-quenched samplesin bulk form are subjected to differential thermal analysis (DTA) to assess the glass transition tempera-ture (Tg), which is 476◦C for pure lithium borate glass. The variations suggest that the structure is beingmodified by the substitution of ZnO.
Structural Investigations of Lithium Vanadoxide Bismo-Borate Glasses
Lithium vanadoxide bismuth borate glasses with composition (30-x)Li 2 O · xV 2 O 5 · 50B 2 O 3 · 20Bi 2 O 3 (x=5, 10, 15) has been prepared with the traditional melt-quenching technique. The density measurements were performed using Archimedes Principal and using density data molar volume was calculated. To determine the oxygen covalency theoretical optical basicity was calculated. To get an idea about the structure FTIR spectroscopy was carried out in the mid-IR region. The spectra revealed absence of boroxol ring and presence of absorption bands corresponding to the combined contributions of tri and tetra borate stretching vibrations. The increasing basicity reveals decrease in the covalence nature of oxygen as we replace the Li 2 O content with V 2 O 5 . The decrease in molar volume may be due to the increase in compactness of the network structure.
IR and EPR studies on some lithium-borate glasses with vanadium ions
Journal of Molecular Structure, 2001
The IR spectra of the xV 2 O 5 (100 2 x)[2B 2 O 3´L i 2 O] glasses contain the bands characteristic for B 2 O 3 (d (B±O± B) 700 cm 21 , n Å(B±O) 1250 cm 21 ), Li 2 O (n Å(Li±O) 415 cm 21 ) and V 2 O 5 (n Å(V±O) 950 cm 21 ) groups. EPR spectra for the glasses with small contents of V 2 O 5 x # 5 mol% show a well-resolved hyper®ne structure typical for isolated vanadyl ions in a ligand ®eld of near octahedral O h symmetry. For x . 20 mol% the EPR spectra may be considered as a superposition of two signals: one with the resolved hyper®ne structure for isolated VO 21 ions in a C 4v symmetry and another broad line without structure at g < 1:96 for associated vanadium ions. The clustered ions are due to the dipole±dipole interactions between V 41 ions and their number increases with the V 2 O 5 content. The spectroscopic studies indicate that the V 2 O 5 oxide becomes a former of the network at high concentration x . 20 mol% together with B 2 O 3 . q