X-RAY-DIFFRACTION INVESTIGATION OF IRON IN SODIUM-PHOSPHATE GLASSES

The short-range order of a series of sodium-iron phosphate glasses has been studied through X-ray diffraction with the purpose of investigat ing the structural role of iron ions in these glasses. Fe-O bond lengt hs and coordination numbers were obtained by simulating the difference radial curves calculated by subtracting the radial distribution funct ion of the proper sodium phosphate glass from those of sodium-iron pho sphate glasses. Good fits were obtained by considering the occurrence of about 10% of Fe2+ and two distinct sites for Fe3+; octahedral coord ination for all iron ions was demonstrated The difference radial curve s show clearly that well-defined structural arrangements extending to medium-range distances form in all the examined cases around iron, whi ch modifies the properties of glasses, by strengthening the cross-bond ing of the phosphate chains.