Transportation pathway of oxygen in the cage-to-cage network of barium-strontium aluminosilicates

Oxygen transport through environmental barrier coating (EBC) to form thermally grown oxide (TGO) on the bond coat greatly affects the service life of the EBC when it is subjected to severe environments. In this work, the oxygen diffusion behaviours through barium-strontium aluminosilicates (BSAS), a typical EBC material, were investigated via ab initio molecular dynamic calculations. The results of these calculations are then verified via isotope exchange experiments. It was found that the interstitial oxygen can stably exist and diffuse through the BSAS. Three interlaced diffusion channels in the structure of BSAS were found to form a complete threedimensional diffusion network. It was also found that the bond length of Si-Al-O can serve as a measure of the diffusion of interstitial molecular oxygen in BSAS. The oxygen permeability of BSAS can be decreased by adjusting the proportions of alkaline earth elements present in the structure, which modifies the bond lengths within the structure. The solution of alkaline earth elements increases the local migration energy barrier, leading to an increase in the overall migration energy barrier.