Raman Spectra Analysis for Calcium Metaphosphate Structure Transformation in Glass Preparation Process

In order to study the structure transformation for the preparation process of calcium metaphosphate glass,the Raman spectra of Ca(H2PO4)2·H2O samples heated from 300 to 1 050 ℃ were collected. The vibration mode was assigned and the length of P-O bonds was calculated by using Raman wavenumber. The results show that the physical chemistry transformation of the Ca(H2PO4)2·H2O occurs as crystal-water and structural water loss,calcium acid pyrophosphate and calcium metaphosphate formation,isomeric change and melting with the increase in temperature. The bend deformation vibrations of P-O could be observed sensitively for the sample heated at high temperature. The P-O bond length in framework increases during the whole polymeric process. The P-O bond length is 0.162 2 nm in the framework for Calcium acid pyrophosphate and 0.164 3 nm for Calcium metaphosphate glass. The P-O bond length decreases in terminal P-O bond during the transformation process from β-Ca2P2O7to γ-Ca(PO3)2 and β-Ca(PO3)2,but keeps unchanged during the Ca(PO3)2 isomeric transformation process.