Studies on the effect of La2O3 and Fe2O3 on the microstructure and high viscosity of CaO-MgO-Al2O3-SiO2 system assisted by quantum chemistry ab initio calculations

To investigate the effects of La 2 O 3 and Fe 2 O 3 on the structure and high viscosity of the CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) glass system, the microstructure was analyzed using in-situ high-temperature Raman spectroscopy, and the viscosity was measured by high temperature hot-stage. A series of cluster models representing aluminosilicate systems modified by La and Fe ions were constructed, followed by geometric optimization and Raman spectral simulation via quantum chemistry ab initio calculations. The results indicates that the effects of La 2 O 3 and Fe 2 O 3 on both vibrational wavenumber and Raman scattering cross-section (RSCS) followed the order: La < (La + Fe) < Fe. The addition of La 2 O 3 and Fe 2 O 3 loose the glass network structure, and led to a progressive rise in the relative content of Q 0 , Q 1 , and Q 2 units, accompanied by a notable decrease in Q 3 and Q 4 units. Consequently, the high viscosity and viscous flow activation energy decrease with the addition of La 2 O 3 and Fe 2 O 3 , but Fe 2 O 3 has a more pronounced effect. Furthermore, based on the NBO/T for characterizing the microstructure, the relationship between viscosity and microstructure is quantitatively analyzed.