THE EFFECTIVE ROLE OF P 2 O 5 ON STRUCTURAL AND MORPHOLOGICAL PROPERTIES OF SiO 2 -CAO-P 2 O 5 DRIED GELS

Abstract: 58SiO2-(38-x) CaO-(x+4) P2O5 dried gels (x=0, 5, 10 and 15mol%) dried gel samples were synthesized at drying temperature 130°C by conventional sol-gel method. For synthesis used precursors are Tetraethyl ortho-silicate (TEOS), Tri ethyle phosphate (TEP), Calcium nitrate tetra hydrate for SiO2, CaO and P2O5 compositions. Structural properties were studied for synthesized dried gels using X-Ray diffraction (XRD), Fourier Transform Infrared (FTIR), Raman spectroscopic analysis and Field Emission Scanning Electronic Microscopy (FESEM) with Energy dispersive X-ray diffraction (EDX) analysis. XRD pattern indicated that all dried gel samples have amorphous nature. FTIR spectroscopic analysis show that more P2O5 content leads to increasing degree of polymerization. Raman spectroscopic analysis indicates that increasing P2O5 content decreases the intensity of orthophosphate structures i.e., increasing P2O5 decreases orthophosphate structural units. Using FESEM average pore sizes of synthesized dried gels are calculated as 143.51, 149.54, 173.25, 182.81 micrometers for corresponding P2O5 mol% of 4, 9, 14 and 19 respectively. From all these observations increasing P2O5 decreases number of orthophosphate units and increases degree polymerization, it leads to increasing pore size on dried gel surface.

Keywords: Sol-gel; P2O5 composition; Calcium oxide; Pore size.