Optical and Conductivity studies of double salt doped Polymer Electrolyte based on Poly Vinyl Alcohol (PVA)
The recent trends in power sources is developing miniature batteries and fuel cells using polymer electrolytes. It is found that the polymers such as PVA, PEO, PVP, PAN etc., doped with ammonium salts or lithium salts have considerable increase in the ionic conductivity of the polymer electrolytes. In the present study, a new combination of electrolytic materials are used and an analysis is made to know the effect of double salt that is Ammonium chloride (NH4Cl) and Sodium Chloride (NaCl) dissolved in equal proportions in various concentrations of Poly Vinyl Alcohol (PVA). The polymer electrolytes are prepared using chlorine salts such as Ammonium Chloride and Sodium Chloride, PVA as host polymer and distilled water as solvent by Solution Casting Technique since this technique is an easy and useful technique. The prepared polymer electrolytes in the form of film, optical properties is studied by using Ultraviolet Visible Spectroscopic technique and ion conducting properties using AC Impedance Spectroscopy technique are studied. It is found that as the concentration of PVA is decreased their viscosity also decreased. From the UV- Visible Spectra the direct and indirect energy gap have been found. In present work, when pure PVA doped with NH4Cl and NaCl the direct band gap and indirect band gap values are 5.57 eV and 5.49022 eV respectively for the highest ionic conducting sample. It is found that band gap value is low for 0.8 PVA: 0.1 NH4Cl: 0.1 NaCl sample. The addition of double salts did not change much the band gap values of the corresponding single salt doped system. AC Impedance Spectroscopic analysis has been used to calculate the dc conductivity. The observed highest conductivity value is in the plateau region which is 4.786 x 10-8 S cm-1 for 1g of PVA doped with 0.1 g of NH4Cl and NaCl each at room temperature which is the highly viscous liquid. It is also observed that when the concentration of PVA is decreased the conductivity value is also decreased. An exponential decay of dielectric constant is in the frequency region log ω = 4.5 to 5.81. Here, there is a sudden hike in the value of Ꜫ’ after which it gradually decreases. But Ꜫ” has a well-defined peak after the surge at log ω equal to 5.81 which may be due to a relaxation phenomenon.