Features of the local structural disorder in Li2O–CaF2–P2O5 glass–ceramics with Cr2O3 as nucleating agent

Li2O–CaF2–P2O5 glasses mixed with different concentrations of Cr2O3 (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS), differential thermal analysis and conventional spectroscopic techniques. The X-ray diffraction and scanning electron microscopic studies reveal the presence of lithium phosphate, calcium phosphate and chromium phosphate (complexes of Cr3+, Cr5+ and Cr6+ ions) crystal phases. The study on DTA suggests that the crystallization is predominantly due to the surface crystallization when the concentration of nucleating agent Cr2O3 is around 0.8 mol%. The IR and Raman spectral studies of these samples indicate that the sample crystallized with 0.8 mol% Cr2O3 is more compact and possesses high rigidity due to the presence of chromium ions largely in tetrahedral positions.