Effect of Barium on Formation and Metastable Structure of Tricalcium Silicate

摘要

The effect of barium on the formation, structure and phase transition of tricalcium silicate(C_3S) has been studied by X-ray powder diffraction combined with Rietveld method, Differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the low contents of barium was favorable the formation of C_3S with up to 1.5% BaO. Higher amounts of BaO inhibited the C_3S crystallization and lead to preferential formation of dicalcium silicate solid solution. Three triclinic forms T1, T2 and T3 of C3S were stabilized. The lattice parameters changed linearly to the barium content, however the discontinuity appeared at the phase transformation boundary, which follows the Vegard's law. The crystallographic structure of T1 and T2 was similar to that of T3. The SiO_4~(4-) tetrahedra were distorted in T1 and T2, while that was approximately regular tetrahedron in T3. The phase transitions of C_3S were influenced by the incorporation of barium. It was believed that the stabilization of high temperature polymorphs of C_3S was related to the lattice distortion caused by ionic substitution.