Optical and Mechanical Properties of Calcium Phosphate
Glasses¹

G. Venkateswara Rao and H. D. Shashikala

Department of Physics, National Institute of Technology Karnataka, Surathkal, Mangalore-575025, Karnataka, India

e-mail: venkatajabili@gmail.com

Received February 19, 2013

Abstract—Binary calcium phosphate glasses in the system, xCaO–(100 – x) P₂O₅ with x = 30, 35, 40, 45, and
50 mol % were prepared by conventional melt quenching technique. The density, molar volume and refractive
index of the glasses were found to increase with the increase in CaO content. Structural investigation by FTIR
spectroscopy revealed that the substitution of P₂O₅ by CaO depolymerizes the phosphate glass network by sys-
tematic conversion of Q³ structural units to Q² structural units by breaking the P–O–P links. From the optical
absorption studies, the optical band gap values were found to decrease with increasing CaO content which can
be due to increase in the concentration of non-bridging oxygens in the glass network. Vickers hardness
increased with the calcium oxide content due to densification. The fracture toughness decreases with the
increase in CaO content due to the increase in the bond density between the modifying cations and the non-
bridging oxygens in the glass network. It was observed that brittleness increases with the addition of CaO con-
tent which can be mainly attributed to the decrease in the molar volume.

Keywords: phosphate glass, optical properties, mechanical properties

DOI: 10.1134/S1087659614030249

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