Sol–gel preparation and high-energy XRD study of (CaO)x(TiO2)0.5−x(P2O5)0.5 glasses (x = 0 and 0.25)
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Glasses from the CaO–TiO2–P2O5 system have potential use in biomedical applications. Here a method for the sol–gel synthesis of the ternary glass (CaO)0.25(TiO2)0.25(P2O5)0.5 has been developed. The structures of the dried gel and heat-treated glass were studied using high-energy X-ray diffraction. The structure of the binary (TiO2)0.5(P2O5)0.5 sol–gel was studied for comparison. The results reveal that the heat-treated (CaO)0.25(TiO2)0.25(P2O5)0.5 glass has a structure based on chains and rings of PO4 tetrahedra, held together by a combination of electrostatic interaction with Ca2+ ions and by corner-sharing oxygen atoms with TiO6 octahedra. In contrast, the (TiO2)0.5(P2O5)0.5 glass has a structure based on isolated P2O7 units linked together by corner-sharing with TiO6 groups. The results suggest that both the dried gels possess open porous structures. For the (CaO)0.25(TiO2)0.25(P2O5)0.5 sample there is a significant increase in Ca–O coordination number with heat treatment.