IARJSET International Advanced Research Journal in Science, Engineering and Technology Impact Factor 7.105Vol. 9, Issue 2, February 2022 DOI: 10.17148/IARJSET.2022.9291 © IARJSET This work is licensed under a Creative Commons Attribution 4.0 International License 602 ISSN (O) 2393-8021, ISSN (P) 2394-1588 Influence of alkali and post transition metal oxide on physical and optical properties of lithium based phosphate glasses N. Hanumantharaju 1 , Karanam Madhavi 2 , Venkatesha Babu K R 3 , S. O Paramesh 4 , V C Veeranna Gowda 5 1,2,5 Department of Physics, Maharani’s Science college for women Palace Road, Bangalore-560001, Karnataka, India. 4 Department of Physics, Vedavathi Government First Grade College, Mysore Road, Hiriyur-577598, Karnataka, India. 3 Department of Physics, Nrupathunga University, Bangalore, Karnataka, India Abstract: Sodium aluminophosphate glasses containing lithium ions of composition X Li 2CO3 - (30-X) Na2 CO3- 60 NH6PO4 -10Al2O3 (where 20 ≤ x ≥ 5) have been prepared by melt quenching technique. The XRD spectra reveal the presence of no sharp peak confirms that the prepared glass samples were of an amorphous nature. The physical and optical properties of the glasses were investigated with the support of density and molar volume. The density of the glass matrix increases with lithium content and its molar volume shows non-linear variation. The metallic and non-metallic nature of the glass was predicted through the calculation of its physical properties. The optical properties of the prepared glass show mole fraction dependent and are mainly dependent on the basicity and polarizability of the Al 2O3 content. The metallization criterion of the glass matrix clearly indicates the size of the conduction and valance band. Optical band gap values were found to decrease from 3.276 to 2.634 eV with aluminium content. The refractive index values were found to increase with lithium content in the glass samples. Inter-nuclear distance, field strength, oxygen packing density, polaron radius, transmission coefficient, reflection loss, dielectric constant and molar refraction were determined to study the physical properties of the glass matrix. Keywords: borate, metallization criterion, XRD, optical band gap. 1. INTRODUCTION The presence of alkali oxides such as lithium, potassium, or sodium oxides as glass modifier in the host phosphate glass improves the physical properties, glass forming capability, and their moisture resistance [1,2]. Besides, alkali fluorides like NaF, LiF, etc. tend to remove the hydroxyl ( –OH) groups from phosphate glasses and form a three dimensional network. Also, it improves the fluorescence but decreases the phonon energy by suppressing the non-radiative losses [3]. Hence, alkali fluorophosphates glass have various applications in solar energy converters, radiation dosimetry, phosphorus, and have good mechanical strength than pure phosphate glasses[4]. High lithium ionic conducting solids are potential electrolyte materials for high energy density batteries and other electrochemical devices [5]. Phosphate glasses have good properties such as high ultraviolet (UV) transmission, high refractive index, low melting temperature, high electrical conductivity, and low glass transition temperature, which make them suitable in technological applications such as optical fibers for communication, luminescent solar energy concentrators, host glasses for solid state lasers, immobilization of nuclear wastes, glass-to-metal sealing and solid state batteries [6–8] but some of the properties like low chemical durability, poor thermal stability against crystallization, volatile and hygroscopic nature of phosphate glasses limit their extensive practical applications. These properties can be enhanced by introducing different metal oxides into the glass matrix [9,10] Aluminium is one of the frequently used oxides which will play an intermediate role between glass modifier and glass former in the glass matrix due to three different coordination numbers [11]. The formation of P–O–Al chains, the Al(OP)4 behave as the glass former, while excess Al 3+ ions lead to Al(OP)6 and behaves as the glass modifier. In the present work we concentrated on behaviour of alkali oxide in aluminophosphate glasses, in which we could see the decrease in density and non-linear variation in molar volume using these values we were in a position to see the variation of physical and optical properties of investigated glass matrix. Also we calculate the refractive index of the glass to check whether it is suitable for optical fiber in communication purpose.