Sol–gel synthesis and structural characterisation of P2O5–B2O3–Na2O glasses for biomedical applications

Abstract

Glasses in the system 40(P₂O₅)–x(B₂O₃)–(60 − x)(Na₂O) (10 ≤ x ≤ 25 mol%) were prepared by the sol–gel technique. A mixture of mono- and diethylphosphates was used as precursor for P₂O₅, boric acid and sodium methoxide were used as source compounds for B₂O₃ and Na₂O, respectively. The dried gels obtained were heat treated at 200, 300 and 400 °C. Structural development occurring during heat treatment and changes with composition were investigated using X-ray diffraction, thermal analysis, infrared spectroscopy, ¹¹B and ³¹P solid state NMR. Systems with x = 20 and x = 25 mol% are amorphous up to 400 °C, whereas systems with lower B₂O₃ content are partially crystalline. This work extends sol–gel preparation of amorphous borophosphate systems having P₂O₅ as the main component.