Chemistry and Materials Research www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.9, 2013 84 Optical Characterization of Polyvinyl alcohol - Ammonium Nitrate Polymer Electrolytes Films Omed Gh. Abdullah 1* , Bakhtyar K. Aziz 2 , and Sarkawt A. Hussen 1 1 Physics Department, School of Science, University of Sulaimani, Iraq. * omed.abdullah@univsul.net 2 Chemistry Department, School of Science, University of Sulaimani, Iraq. Abstract Polyvinyl alcohol – Ammonium Nitrate polymer electrolyte films were prepared by casting method. UV-Vis Double Beam Spectrophotometer in the wavelength range (190-1100) nm were used to investigate the optical properties. The optical constants such us, transmission spectra, refractive index, extinction coefficient, real and imaginary parts of the dielectric constant, optical band gaps, and optical conductance are found. It was found that the energy band gaps are decreased upon the increase of salts concentration. The values of the width of the tails of localized states in the forbidden gap of the films obtained from Urbach plots are varied from 0.64 to 1.16 eV. The real and imaginary part of dielectric constant of the polymer electrolyte films increases with increasing NH 4 NO 3 concentration. The dielectric constant shows decreases abruptly in the wavelength (235-260) nm, and finally becomes constant with increase wavelength. Keywords: optical energy band gap; optical conductance; refractive index; extinction coefficient. 1. Introduction Polymer electrolytes recently have been a subject of great interest due to theoretical interest as well as practical importance for the development of electrochemical devices, such as rechargeable batteries, capacitors and sensors [1]. Generally, the addition of inorganic salts into a polymer matrix can improve its conductivity. It was found that metallic salts with Polyvinyl Alcohol (PVA) can improve the electrical conductivity, optical absorption and of the refractive index [2]. Polyvinyl Alcohol (PVA) exhibits adhesive and good film-forming properties. So an intense research has been focused both from a fundamental point of view in understanding the mechanism of ion transport and also from the application point of view in enhancing the performance of devices based on polymer electrolytes [3]. The present work aims to study the effect of Ammonium Nitrate (NH 4 NO 3 ) on the optical properties of PVA. 2. Experimental details Different compositions of Polyvinyl alcohol (PVA) Ammonium Nitrate (NH 4 NO 3 ) films have been prepared by solution techniques, using different weight ratios of NH 4 NO 3 (0, 5, 10, 15, 20, and 25) wt%. The solution of PVA and NH 4 NO 3 is obtained by dissolving them in distilled water at 350 K, and the solution is stirred well using magnetic stirrer for one hour, until highly homogenous polymer solution was formed. These homogenous solutions were casted in a glass dish (diameter of 5 cm). The whole assembly was placed in a dust free chamber and the solvent was allowed to evaporate slowly in open air at room temperature for a week. The thickness of the films were in the range of (0.045-0.10) mm. 3. Theoretical method The ratio of radiant power transmitted ( ) by a sample to the radiant power incident ( ) on the sample is called the transmittance : but, Where is the sample thickness, and is the optical absorption coefficient, which calculated from absorbance ( ), and thickness of the films by [4, 5]: If is the Transmittance and is the absorbance of the films, then, the reflectance of the films has been calculated as follows [6]: The refractive index , and extinction coefficient ,of the film, are calculated using [7, 8]: