Roles of P2O5 Addition on the Viscosity and Structure of CaO-SiO2-Al2O3-Na2O-P2O5 Melts

In this research, the effect of P2O5 additions on the viscosity of CaO-SiO2-Al2O3-Na2O-P2O5 melts was clarified using rotating cylinder method. In addition, the role of P2O5 on the microstructure of these melts was investigated by Raman, Fourier Transformation Infrared (FTIR) and Magic Angular Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopic techniques. We found that an increase of P2O5 content continuously increased the viscosity of melts and meanwhile increased the apparent activation energy for the viscous flow. The FTIR and Raman results show that the degree of polymerization (DOP) got increased with more P2O5 additions and this was consistent to the variation trend of melt viscosities. The MAS-NMR results show that there exist two kinds of PO4 tetrahedron, namely, Q(0)(P) and Q(1)(P), in the samples and a transformation appeared between them with increasing P2O5 content. The present study thus provided significant clues for stabilizing the pore structures in foam glass ceramics.