Optical and mechanical properties of calcium phosphate glasses

Abstract

Binary calcium phosphate glasses in the system, xCaO-(100 - x) P <inf>2</inf>O<inf>5</inf> 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 P<inf>2</inf>O<inf>5</inf> by CaO depolymerizes the phosphate glass network by systematic 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 content which can be mainly attributed to the decrease in the molar volume. © 2014 Pleiades Publishing, Ltd.