Structural study, thermal and physical properties of K2O-CaO-P2O5 phosphate glasses

Glasses of 50P2O5-xCaO-(50-x)K2O (x= 0, 10, 20, 30, and 40 mol %) compositions were synthesized using the melt-quench procedure. The amorphous character of the prepared material was confirmed by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Fourier Transform Infra-Red (FT-IR) and Raman spectroscopy are also carried out in order to determine the structural network evolution of the glassy materials with the composition. Besides, the physical properties of the glassy phosphate system were examined such as density and molar volume. The results showed that the increase of CaO content in phosphate glasses diminish the molar volume and raise the density and transition temperature. FTIR and Raman spectroscopy analysis demonstrate the formation of P-O-Ca bonds that substitute P-O-K bonds and the depolymerization of the phosphate chains. The formation of P-O-Ca bonds is in accordance with variations of glass transition temperature, (Tg), molar volume (Vm) and density (ρ). The former bonds are the origin of the partial glass-forming ability of Ca2+. In addition, an analysis of the surface morphology features was conducted using a Scanning Electron Microscopy (SEM) technique