Atomic Structure Of Sodium Iron Phosphate Glasses

The atomic structure of a series of sodium iron phosphate glasses is studied using different experimental techniques: X-ray and neutron diffraction (ND), infrared spectroscopy, extended X-ray absorption fine structure (EXAFS), and X-ray absorption near-edge structure (XANES). Detailed information about the atomic pair correlations is obtained. The high resolution of ND in real space resolves two P-O distances at 1.48 A and 1.59 A as expected. All the glasses are found to consist of a phosphate tetrahedral network with metaphosphate chains and pyrophosphate units, and every phosphate unit is found to have two or three nonbridging oxygen (NBO) links available to coordinate with Na and Fe cations. The Fe-O coordination number in these glasses is found to decrease from 5.7 to 4.8 with increasing the Fe content, whereas the Na coordination number of approximately 5 is detected for all the samples.