Effect of gadolinium doping on phase transformation and microstructure of Gd2O3-Y2O3-ZrO2 composite coatings prepared by electrophoretic deposition

4 mol.% Y2O3 stabilized ZrO2 (YSZ) doped with various quantities of Gd2O3 (G-YSZ) ceramic coatings were synthesized by electrophoretic deposition method, and followed by vacuum sintering and isothermally annealing at 1000 °C for different durations. X-ray diffraction (XRD) was used to investigate their phase composition. Scanning electron microscopy (SEM) was employed to examine their microstructure, while energy dispersive X-ray spectrometer (EDS) was used to assess composition of the composite coatings. The results indicated that YSZ coating was composed of tetragonal and monoclinic phase after vacuum sintering at 1000 °C for 2 h under vacuum (<10−3 Pa). G-YSZ composite coatings were composed of tetragonal, monoclinic phase and a small amount of Gd2Zr2O7 phase after vacuum sintering at 1000 °C for 2 h, whereas the content of monoclinic phase in G-YSZ composite coatings increased with increasing Gd2O3 concentration. It was found that G-YSZ composite coatings were composed of tetragonal ZrO2 phase, monoclinic ZrO2 phase and cubic phase, whereas Gd2Zr2O7 phase disappeared, after G-YSZ composite coatings were isothermally annealed at 1000 °C in air for 100 h. A detailed description of the results and their discussion was presented in the paper.