Structures of Iron-Lithium-Calcium-Silicate Glass and its Devitrified State

The structure of SiO 2 -Li 2 O-CaO-Fe 2 O 3 glass is studied by neutron diffraction together with Reverse Monte Carlo simulation as well as by Raman and Extended X-ray Absorption Fine Structure spectroscopy. In order to check for the extent to which iron oxide can be successfully included in the glass, 15 mol% iron was tried but resulted in partial devitrification. Average local structure parameters are presented. The first neighbour distances were found to be independent of concentration within the limits of error: r Si-O = 1.60 Å; r Fe-O = 1.90 Å; r Li-O = 1.95/2.0 Å and r Ca-O = 2.30 Å. Tetrahedral units of Si(O) – from SiO 2 - and Fe(O) – from Fe 2 O 3 - with average coordination numbers 3.48 and 4.59 respectively, were found. Raman spectral analyses show the Q 1 and Q 2 connections to be more numerous (~50%) for the purely glassy (10Fe), than for 15Fe (~60%), with Q 3 connections occurring twice as often (~35%) for the glass as the devitrified sample (~17%). Thus, the devitrified sample may have a more open structure capable of accommodating Fe ions in nano-sized iron-rich regions as indicated by the RMC.