The structure of phosphate glass biomaterials from neutron diffraction and ³¹P nuclear magnetic resonance data

Neutron diffraction and ³¹P nuclear magnetic resonance spectroscopy were used to probe the structure of phosphate glass biomaterials of general composition (CaO)_0.5-x(Na₂O)_x(P₂O₅)_0.5 (x = 0, 0.1 and 0.5). The results suggest that all three glasses have structures based on chains of Q² phosphate groups. Clear structural differences are observed between the glasses containing Na₂O and CaO. The P-O bonds to bridging and non-bridging oxygens are less well resolved in the neutron data from the samples containing CaO, suggesting a change in the nature of the bonding as the field strength of the cation increases [Formula: see text]. In the (CaO)_0.5(P₂O₅)_0.5 glass most of the Ca²⁺ ions are present in isolated CaO_x polyhedra whereas in the (Na₂O)_0.5(P₂O₅)_0.5 glass the NaO_x polyhedra share edges leading to a Na-Na correlation. The results of the structural study are related to the properties of the (CaO)_0.4(Na₂O)_0.1(P₂O₅)_0.5 biomaterial.