Md. Shareefuddin

Ionic conductivity and battery characteristic studies on PEO+AgNO3 polymer electrolyte

Abstract A new Ag + ion conducting polymer electrolyte based on PEO+AgNO 3 system is reported. The solvation of Ag + ion with PEO is confirmed by XRD studies. The electrical conductivity and cell discharge characteristics at room temperature (32°C) are reported. The highest conductivity (9.2×10 −3 S cm −1 ) has been observed for 80:20 composition (i.e. Ag + / E 0 =0.6). An electrochemical cell with the configuration Ag/PEO+AgNO 3 / (I 2 +C+electrolyte) has also been studied [for which open circuit voltage (OCV)=610 mV and short circuit current (SCC)=4.4.×10 −6 A] and a number of cell parameters obtained are reported.

Electron spin resonance and optical absorption spectra of Cu2+ ions in xNaI(30 - x)Na2O70B2O3 glasses

Electron spin resonance (ESR) and optical absorption spectra of xNaI(30 - x)Na2O70B2O3 glasses containing 1 mol% CuO have been investigated at room temperature. The optical absorption spectra of all the glass samples exhibited a broad asymmetric absorption band which correspond to the d—d transitions bands due to Cu2+ ions. From the ESR spectra the spin-Hamiltonian parameters were evaluated. It was observed that the ground state of Cu2+ is dx2 - y2 orbital and the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The bonding co-efficients were evaluated using the optical and ESR data to obtain information about Cu2+-ligand bond nature. The basicity of σ-type symmetry was independent of the glass composition while the π-type basicity was found to vary as a function of the glass composition.

Ac response of polycrystalline sodium yttrium fluoride

Abstract Ac response of polycrystalline sodium yttrium fluoride (NaYF 4 ) has been studied in the temperature region of 350–950 K and in the frequency range 50 Hz–100 kHz using blocking electrodes. From the admittance plots, the bulk conductivity (σ), dielectric constant (ϵ′) and loss angle (tan δ) were determined at different temperatures and frequencies. The conductivity was found to increase with increasing temperature. Large value of ϵ′ observed at high temperatures was attributed to space charge polarization effects. The relaxation character of tan δ was observed. Theac conductivity was found to increase with increasing frequency.

Electron paramagnetic resonance study of vanadyl ions in Nal-Na2O-B2O3 glasses

Electron paramagnetic resonance (EPR) studies of glasses doped with transition metal ions have been used to obtain information about the glassy network and to identify site symmetry around the transition metal ion [1]. There has been considerable interest in the physical properties of alkali halo borate glasses because of their fast ionic conductivity [2-4]. In this letter we report the EPR studies of the transition metal ion VO 2+ in the alkali halo borate glass system xNaI-yNa20-70B203. The starting materials used were analar grade reagents of boric acid (H3BO3), sodium carbonate (NazCO3) and sodium iodide (NaI). The amounts were calculated to form 10 g of each glass. Each batch was first sintered at about 723 K then melted in a porcelain crucible in an electrically heated furnace at a temperature of 1173 K. The melts were quenched at 473 K in air by pouring them onto a stainless steel plate which was maintained at 473 K. The glasses were annealed for 24 h at the same temperature to relieve the mechanical stress. To each batch 1 mol % of 702+ was added in the form of 7205 as paramagnetic probe. Table I gives the glass composition in mol %. X-ray power patterns revealed the TABLE I Composition of the glasses Composition (%)

Mixed alkali effect in the physical and optical properties of xK2O-(25-x)Na2O-12.5MgO-12.5BaO-50B2O3 glasses

Abstract Borate glasses with the composition xK2O-(25-x)Na2O-12.5MgO-12.5BaO-50B2O3 (x = 0, 5, 10, 15, 20 and 25 mol%) were prepared by the melt-quenching technique and were characterized using X-ray diffraction at room temperature. From the optical absorption spectra, the direct forbidden, direct allowed, indirect allowed, and indirect forbidden energy gaps; Urbach energy; refractive index (n); dielectric constant (ɛ); reflection loss (R); molar refraction (Rm); and molar polarizability (αm) values of all of the glass samples were evaluated. Rm, αm and Λth increase with the increase of the K2O content. The values of R, ɛ and n increase up to x = 10 mol% and then decrease above x = 10 mol%, which may be due to the mixed alkali effect. The density and molar volume values show the opposite behaviour and vary nonlinearly with the K2O content, which manifests the mixed alkali effect in the present glass system. The infrared (IR) spectra of the borate glasses reveal the existence of 3- and 4-coordinated boron atoms. The specific vibrations of the Na-O, K-O, Mg-O, and Ba-O bonds were observed in an IR study.

Solid state battery with pure and doped sodium yttrium fluoride as the solid electrolyte

Solid state batteries using pure and doped sodium yttrium fluoride as the solid electrolytes were fabricated at ambient temperature. The discharge characteristics of the cells for a load of 1 M Omega were studied. The cell with NaYF4:Dy as the solid electrolyte exhibited a larger plateau region compared with the other cells. Open circuit voltage and short circuit current of the cells range from 2.5 to 2.7 V and 7 mu A to 435 mu A respectively. The performances of the cells under varying loads for a constant voltage of 1.5 V were also investigated. Various cell parameters were evaluated.

Complex admittance study of potassium yttrium fluoride

Abstract The complex admittance of pure and 0.5 mol% sodium doped potassium yttrium fluoride polycrystalline pellets, between two inert blocking electrodes, was studied from 300 to 950 K in the frequency range 50–100 kHz. In most cases the admittance plot exhibited a depressed circular arc in the low frequency region and a straight line in the high frequency region. The bulk conductivity σ, the dielectric constant e′ and the loss angle tan δ were determined from the admittance plots. The high values of e′ observed at high temperatures were attributed to space charge polarization effects. The a.c. conductivity was found to increase with increasing frequency.

Ionic transport and battery characterization studies of barium-doped potassium yttrium fluoride

Abstract Pure and barium fluoride doped potassium yttrium fluoride materials were synthesized using the solid state reaction method and were characterized by X-ray diffraction, transference number and transient ionic current measurements. In all the samples the conductivity was found to be mainly ionic while the electronic conductivity was found to be small. Solid state batteries were fabricated in the configuration K/electrolyte/(I2 + C + electrolyte) with KYF4 and KYF4: BaF2 as the solid electrolytes. Their discharge characteristics were studied for a load of 100 K Ω at 313 K. Open circuit voltage (OCV) and short circuit current (SCC) of the cells range from 2.38 to 2.82 V and 650 to 2340 μA, respectively. Various cell parameters were evaluated.

Ionic transport and battery characterization studies on 15NaF-15Na2O-70 [(1 − x)B2O3 − xCr2O3] quaternary glassy systems

Abstract Glasses in the quaternary system 15NaF-15Na 2 O-70-[(1 − x ) B 2 O 3 - xCr 2 O 3 ] have been prepared by a melt quenching method and characterized by X-ray diffraction, differential scanning calorimetry (DSC) and electrical conductivity. The conductivity was found to vary in a non-linear manner with the composition x . The highest conductivity composition glass was used as an electrolyte in the fabrication of a solid state cell. Its discharge characteristics were investigated at ambient temperature. The open circuit voltage of the cell was found to be 2.6 V while the short circuit current was 1000 μA. Various cell parameters were evaluated.

Thermally stimulated depolarization current studies in sodium- and barium-doped potassium yttrium fluoride

Abstract The results of thermally stimulated depolarization current (TSDC) and electrical conductivity studies of potassium yttrium fluoride (KYF4) compound doped with sodium and barium are presented. The TSDCs were measured as a function of the polarizing temperature and polarizing field strengths at a constant heating rate of 0.09 K s−1. The conductivity studies were carried out in the temperature range 370–835 K with different dopant concentrations. The variation of the conductivity with the doping concentration was found to be non-linear. The relaxation parameters and the activation energies were evaluated. The origin of the TSDC peak in KYF4:Na was attributed to space charge polarization. However, in the case of KYF4:Ba, in addition to space charge polarization, there is also a small contribution from the dipolar mechanism.