S. Austin Suthanthiraraj

FT-IR spectroscopic investigation of ionic interactions in PPG 4000: AgCF3SO3 polymer electrolyte.

The effect of salt concentration on the ubiquitous ionic interactions observed in the case of the silver ion conducting polymer electrolyte system poly(propylene glycol) (PPG)-silver triflate has been investigated using Fourier transform infrared (FT-IR) spectroscopy as a probe for the characterization of the local environment of the triflate ion in PPG-based polymer electrolytes. The maximum free anion concentrations of symmetric and asymmetric SO(3) stretching modes in the case of poly(propylene glycol) complexed with silver triflate (AgCF(3)SO(3)) corresponding to the ether oxygen metal cation ratios from 2:1 to 6:1 have been investigated in detail. The present Fourier transform infrared spectral studies of the C-O-C stretching mode have shown reduction in the intensity, due to the decrease of salt concentration. The splitting of vibrational modes has been analyzed in terms of free ions, ion pairs and aggregates. The bands of SO(3) symmetric stretching mode appearing at 1032 and 1038 cm(-1) in the chosen polymer electrolyte material have been assigned to free ions and ion pairs respectively.

Preparation and transport studies of the new superionic system (CuI)x·[(Ag2O)3·(B2O3)]100−x (35 ⩽x⩽75)

Abstract Efforts were made to prepare high conductivity superionic solids in the mixed system (CuI)x·[(Ag2O)3·(B2O3]100−x where x= 35, 40, 45, 50, 55, 60, 65, 70 and 75 mol% respectively, by melting the appropriate solid mixtures and then quenching them to low temperatures. Powder specimens of these compositions were analysed using differential scanning calorimetric (DSC) and X-ray diffraction (XRD) techniques. These studies have confirmed the formation of new products as revealed by the absence of diffraction peaks of parent materials in the XRD patterns. Among the various compositions, a significant number are found to contain AgI since DSC traces have indicated the characteristics β-α-phase transition temperature of AgI around 420 K. Detailed temperature-dependent electric conductivity studies on these materials by ac impedance analysis in the frequency range 65.5 kHz1 Hz and over the temperature range 293–398 K have clearly indicated the occurrence of high silver ionic conductivities. It is found that the highest electrical conductivity of 2.14×10−3Scm−1 and a silver ion transport number of 0.96 at 305 K could be achieved for the composition, 40 CuI45 Ag2O15 B2O3 which exhibits a low activation energy of 24.1 kJ/mole in the temperature range of investigation.

Impedance and modulus spectroscopic studies on the fast ion conducting system CuIAg2MoO4

Abstract This paper deals with a detailed analysis of impedance ( z ) and conductivity (σ) spectra, as well as modulus ( M ) diagrams of the mixed system CuIAg 2 MoO 4 , exhibiting Ag + ionic conductivity over the temperature range 290–400 K and in the frequency range, 65.5 kHz-1 Hz. The observed conductivity spectra could be attributed to Jonschers power law dependence. Impedance spectra have enabled the separation of bulk properties from electrode effects. The modulus spectra have exhibited a long tail pattern in the low frequency region and a tendency to peak at higher frequencies thereby suppressing the electrode effects at low frequencies in the modulus formalism. A comparative study of modulus spectra and the impedance patterns has indicated the non-Debye type of frequency dispersion in the mixed system.

Frequency response analysis of the fast ion conducting system cuprous iodide - silver chromate

Abstract Preparation and characterization of new superionic conductors have been considered to be an essential component in the area of solid state ionics. The details of frequency response analysis carried out in terms of impedance (Z), conductivity (σ) and modulus (M) diagrams on a series of compositions in the mixed system CuIAg 2 CrO 4 exhibiting Ag + ionic conductivity over the temperature range 290–400 K and in the frequency range 65.5 kHz–1Hz are presented in this paper. The frequency - dependent conductivity spectra have been found to obey the Jonschers power law over the temperature range under investigation. The observed temperature dependence of conductivity has indicated that a low activation energy is associated with the composition possessing high conductivity and vice versa. The separation of grain - boundary and electrode polarisations from the bulk impedances has been made feasible through the impedance spectra. A long tail in the low-frequency region and a tendency to peak at higher frequencies in the modulus diagram have shown that it is possible to effectively suppress the information concerning grain-boundary and electrode effects in the modulus formalism. Modulus and impedance spectra have indicated the non-Debye type of polarisation in the above material.

Synthesis, thermal and solar cell application of novel hyperbranched polyurethanes containing azomethine and aryl-ether connectivities

Bis-{[(4-hydroxybutoxyphenyl)methylidene]aminophenoxyhexyl}benzene-1,3-dicarboxylate – a novel A2 diol monomer – and a series of new blocked isocyanates (B3 monomers) were synthesized in high yield and their structures were confirmed. Using these monomers, different hyperbranched polyurethanes (HBPUs) containing azomethine and aryl-ether connectivities were prepared via an A2 + B3 approach. All possible parameters were varied to study their effect on molecular weight build-up. The effects of concentrations of A2 and B3 and the A2: B3 monomer ratio were well reflected in the molecular weight of the polymer. The structure of the B3 monomer was also found to have a significant effect on the molecular weight. The polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and impedance spectroscopy. All the polymers registered unusual sub-T g; and they invariably underwent decomposition at three distinct stages with significantly improved thermal stability at initial stage. The ionic conductivity of HBPU increased remarkably upon doping with KI and I2. The dye-sensitized solar cell fabricated using this polymer as electrolyte yielded an overall conversion efficiency of 3.5% upon illumination with visible light.

Molecular structural analysis of 55mol% CuI-45mol% Ag2MoO4 solid electrolyte using XPS and laser raman techniques

The solid electrolyte 55 mol% CuI - 45 mol% Ag2MoO4 has been analyzed structurally by employing X-ray photoelectron spectroscopic (XPS) and laser Raman studies. The core level Ag 3d, Cu 2p, Mo 3d, I 3d and O1s XPS spectra of the constituent elements were recorded. The presence of both bridging (BO) and non-bridging (NBO) oxygen atoms in the oxyanion framework has been identified through the deconvolution of the O 1s spectrum. Laser Raman spectroscopic studies tend to reveal that the oxyanion framework is constructed with [MoO42−]-tetrahedral and [MoO6]-octahedral units as in the case of CuI - Cu2MoO4 and AgI - Ag2O - MoO3 glasses.

Preparation and characterization of superionic materials in a new mixed system (Cu(1−x)AgxI)–(Ag2O)–(P2O5), (0.05≤x≤0.25)

Abstract In this paper attempts have been made to prepare superionic glassy electrolytes in the mixed system 30(Cu (1− x ) Ag x I)–46.66(Ag 2 O)–23.33(P 2 O 5 ), where x =0.05, 0.1, 0.15, 0.2 and 0.25, respectively, using the melt quenching process. The solid samples were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy and silver ionic transport number studies. XRD analysis and FT-IR spectroscopic results have provided details regarding the various phases present in the new system and also indicated the formation of composite materials consisting of glassy and crystalline phases. The transport number measurements have indicated the formation of superionic solids having Ag + ions as the mobile species in the present system.

Compositional effect of ZrO2 nanofillers on a PVDF-co-HFP based polymer electrolyte system for solid state zinc batteries

Composite polymer electrolytes (CPEs) comprising poly(vinilydene fluoride-hexafluoro propylene), PVDF-co-HFP and zinc triflate, Zn(CF3SO3)2 with varying concentrations of ZrO2 nanofillers were prepared by solution casting technique with N,N-dimethyl formamide (DMF) as the common solvent. The polymer electrolyte specimen with the particular composition 75 wt% PVDF-co-HFP: 25 wt% ZnTf + 7 wt% ZrO2 showed the highest conductivity of 4.6 × 10-4 S/cm at 298 K as confirmed from impedance measurements and favored by the rich amorphous phase of the CPE revealed from room temperature X-ray diffraction analysis (XRD). The electrical conductivity relaxation time and its distribution within the materials have been evaluated from the electric modulus M″ and impedance Z″ data which showed the occurrence of non-Debye type of relaxation phenomenon. The changes in the surface morphology of the CPEs were examined using scanning electron microscopy (SEM). The electrochemical stability window of CPE is found to be 2.6 V with a thermal stability up to 300 °C. An electrochemical cell has been fabricated based on Zn/MnO2 electrode couple under a constant load of 1 MΩ and its discharge characteristics have been evaluated.

Enhanced performance of a nanocrystalline dye-sensitized solar cell based on polyurethane dendrimers

The use of novel p-chlorophenyl and styrenyl-TEMPO terminated fourth generation (G4) polyurethane dendrimers doped with KI and I2 in conjunction with N3 dye as an efficient polymer electrolyte to improve the efficiency of nanocrystalline TiO2 dye-sensitized solar cell (DSSC) is described. Coordinative interactions and structural changes of these dendritic polymer electrolytes have been characterized by X-ray diffraction (XRD), electrical conductivity and scanning electron microscopic (SEM) studies. The XRD and SEM results confirm the amorphous structure of the electrolytes. The ionic conductivity of doped polyurethane dendrimers was remarkably high and the values were in the range of 1.5 × 10−3 Scm−1 to 1.1 × 10−3 Scm−1 at room temperature. As a consequence, the performance of the devices fabricated with dendrimers were appreciably good compared to that fabricated without dendrimers and in one case the photocurrent, photovoltage, fill factor and energy conversion efficiency achieved were 10.6 mA cm−2, 900 (mV), 0.51 and 8.5%, respectively, under simulated sunlight with AM 1.5 at 50 mW cm−2.

Bonding characteristics in silver vanadate: an XPS study☆

Abstract Using X-ray photoelectron spectroscopy (XPS), the qualitative and quantitative analyses of silver and vanadium in silver vanadate have been carried out. It is concluded that the covalent character of the oxide ions may be responsible for Ag 3 VO 4 with silver iodide to function as a superionic conducting glass. The implications are discussed.