Microstructure evolution and hot corrosion mechanisms of Ba2REAlO5 (RE = Yb, Er, Dy) exposed to V2O5 + Na2SO4 molten salt

Ba2REAlO5 (RE = Dy, Er, Yb) powders were synthesized by a solid state reaction method, followed by cold pressing and sintering to produce pellets for hot corrosion tests. When exposed to V2O5 + Na2SO4 molten salt at 900 °C and 1000 °C for 4 h and 20 h, REVO4, Ba3(VO4) 2 and BaAl2O4 formed as corrosion products due to chemical interactions between the ceramics and the molten salt, which were temperature and time independent. After the hot corrosion tests at 1000 °C, continuous, dense reaction layers with a thickness of ∼80 μm formed on the sample surfaces, which had an effective function on suppressing further penetration of the molten salt. The hot corrosion mechanisms of Ba2REAlO5 are proposed based on Lewis acid-base rule, phase diagrams and thermodynamics. From a thermodynamics perspective, the molten salt directly reacting with Ba2REAlO5 is difficult compared with Yb2O3, Al2O3 and BaO.