V. V. R. Narasimha Rao

Optical and Electrical Properties of Pure and Doped PEO Polymer Electrolyte Films

A sodium ion conducting polymer electrolyte based on polyethylene oxide (PEO) complexed with NaFeF4 was prepared using solution cast technique. The complexation of the salt with PEO was confirmed by X‐ray diffraction (XRD) and infared spectroscopic (FTIR) studies. Optical absorption studies were made in the wavelength range 200–600 nm on pure and NaFeF4 doped PEO film. The absorption edge was observed at 4.62 eV for undoped PEO while it ranged from 3.86 to 3.61 eV for NaFeF4 doped films. The direct band gaps for undoped and NaLaF4 doped PEO films were found to be, respectively, 4.54 and 3.74, 3.63 and 3.54 eV while the indirect band gaps were 4.43 and 3.52, 3.38 and 3.26 eV, respectively. It was found that the energy gaps and band edge values shifted to lower energies on doping with NaFeF4 salt. Electrical measurements were made in the temperature range 300–370 K as a function of dopant concentration. The nature of charge transport in this system was determined using Wagners polarization technique and was found to be predominantly due to ions.

Investigations on Structural and Electrical Properties of KClO4 Complexed PVP Polymer Electrolyte Films

Potassium ion-conducting polymer electrolytes based on poly (vinyl pyrrolidone) (PVP) complexed with KClO4 were prepared using a solution cast technique. These samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Differential Scanning Calorimetry (DSC), and impedance spectroscopy. The complexation of the salt with polymer was confirmed by FT-IR and XRD studies. The ionic conductivity was found to increase with increasing temperature and salt concentration. The highest ionic conductivity (0.91 × 10−5 S/cm) and low activation energy (0.29 eV) was obtained for the polymer complexed with 15 wt% KClO4 among all the compositions.

Effect of Complexation of NaCl Salt with Polymer Blend (PEO/PVP) Electrolytes on Ionic Conductivity and Optical Energy Band Gaps

Sodium ion conducting polymer blend electrolyte films, based on polyethylene oxide (PEO) and poly vinyl pyrrolidone (PVP) complexed with NaCl salt, were prepared using solution casting technique. The complexation of the salt with the polymer blend was confirmed by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR) and UV‐vis spectroscopy. Frequency and temperature dependence of electrical conductivity of the films was studied with impedance analyzer in the frequency range of 1 Hz to 1 MHz and in the temperature range of 303–348 K. UV‐vis absorption spectra in wavelength region 200–800 nm, were used to evaluate the optical properties like direct and indirect optical energy band gaps, optical absorption edge. The optical band gaps decreased with the increase of Na+ ion concentration. This suggests that NaCl, as dopant, is a good choice to improve the electrical and optical properties of PEO/PVP polymer blend electrolytes.

Thermally stimulated discharge currents in polyvinyl pyrrolidone polymer films

Abstract Polyvinyl pyrrolidone films of thickness 17.6 μm were grown by the isothermal solution growth technique. Thermally stimulated discharge currents were studied on these films as a function of polarizing field strength and polarizing temperature, at a constant heating rate of 0.14 Ks −1 . In all these studies only one TSDC peak was observed and the temperature corresponding to this peak was found to show weak but definite dependence on the polarizing field strength and polarizing temperature. The activation energies and relaxation parameters and charge associated with this peak were evaluated. The origin of TSDC was attributed to the space charge process.

Studies on electrical and optical properties of PVP:KIO4 complexed polymer electrolyte films

Solid polymer electrolytes based on poly (vinyl pyrrolidone) (PVP) complexed with potassium periodate (KIO4) salt at different weight percent ratios were prepared using solution- cast technique. X- ray diffraction (XRD) results revealed that the amorphous nature of PVP polymer matrix increased with the increase of KIO4 salt concentration. Electrical conductivity was measured with an AC impedance analyzer in the frequency and temperature range 1 Hz-1 MHz and 303 K-373 K respectively. The maximum ionic conductivity 1.421×10−4Scm−1 was obtained for 15 wt% KIO4 doped polymer electrolyte at room temperature. The variation of ac conductivity with frequency obeyed Jonscher power law. Optical absorption studies were performed in the wavelength range 200-600 nm and the absorption edge, direct band gap and indirect band gap values were evaluated.

Ionic transport studies of PVP: KBrO4 complexed polymer electrolyte films

Solid Polymer electrolytes based on Poly (vinyl pyrrolidone) (PVP) complexed with KBrO4 at different weight percent ratios were prepared using solution cast technique. The complexation of the salt with the polymer was confirmed by Fourier transform infrared (FT-IR) spectroscopy studies. Electrical conductivity was measured with an AC impedance analyzer in the frequency and temperature range 1Hz-1MHz and 303-403K respectively. The variation of ac conductivity with frequency obeys Jonscher power law. The nature of the charge carriers in these polymer electrolyte films was determined by Wagners polarization technique. This data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions. Using these polymer electrolytes, electrochemical cells were fabricated and their discharge characteristics were studied.

Development of a new polymer electrolyte (PMMA-CO-P4VPNO+KClO3) for solid state electrochemical cells

Polymer electrolyte films based on a co-polymer polymethyle methacrylate-co-poly 4vinyl pyridine N-oxide (PMMA-CO-P4VPNO) complexed with KClO3 were prepared by solution cast technique. The complexation of KClO3 salt with the polymer was confirmed by infrared studies. Measurements of the dc conductivity in the temperature range 300–410 K and transference numbers were carried out to investigate the charge transport in the polymer electrolyte system. Transference number data show that the charge transport in this polymer electrolyte system is predominantly due to ions. Using the polymer electrolyte solid state electrochemical cells were fabricated with the configuration (K)-(PMMA-CO-P4VPNO+KClO3)-(I2+C+electrolyte) and various parameters of the cells including open circuit voltage (OCV) and short circuit current (SCC) were evaluated.