A comparative study on the hot corrosion behavior of plasma sprayed Sm/Gd doped La2Zr2O7/YSZ and Sm and Gd co-doped La2Zr2O7/YSZ coatings

Abstract

Gd2O3 and Sm2O3 co-doped LZ ceramic ((La0.5Gd0.25Sm0.25)2Zr2O7/YSZ) are designed and prepared by atmospheric plasma spraying (APS). It is the aim of this study to investigate the similarities and differences between co-doped sample and mono-doped samples, (La0.5Gd0.5)2Zr2O7/YSZ and (La0.5Sm0.5)2Zr2O7/YSZ on hot corrosion behaviors exposed to Na2SO4 + V2O5 molten salts. Thermodynamic calculations are used to predict the hot corrosion mechanism before experiments. Characterization and hot corrosion behavior are analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). Results indicate that the main hot corrosion products are composed of rare-earth vanadates ((La, Gd)VO4, (La, Sm)VO4 and (La, Gd, Sm)VO4, respectively) and ZrO2. After 10 h of corrosion, the reaction layer evolves into trilayered structure containing Zr-rich layer, V-rich layer and mixed-layer. The formation mechanism is discussed in detail. The co-doped sample exhibits excellent degradation resistance, which can be attributed to the higher entropy value. The formation of the particular trilayered structure occurs earlier in the co-doped sample, which also provides a role in reducing the degradation rate of ceramics.