Structural Role of Strontium Oxide in Modified Silicate Glasses

Glasses in the system 24.5Na 2 O.24.5CaO.6P 2 O 5 .xSrO.(45-x)SiO 2 have been studied in the composition region of x = 0–15 mol%. The as-prepared glasses are transparent and have an amorphous network structure. On the other hand, heat-treated glasses are transformed to opaque white glass-ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca 3 (PO 4 ) 2 ), wollastonite (calcium silicate, CaSiO 3 ), and strontium calcium phosphate [Ca 2 Sr (PO 4 ) 2 ) are the main well-formed crystalline species that played the major role in material bioactivity. Increasing SrO leads to enhancing material crystallite and enhances the hardness of the host glass matrix. The change of XRD spectra, 31 P NMR chemical shift, and hardness number upon increasing SrO are considered due to modification of the apatite Ca(PO 3 ) 2 to involve Sr ions inducing Ca 2 Sr (PO 4 ) 2 apatite one. Such species play the role in enhancing material properties and hardness.