Effect of doping CeO2 and Sc2O3 on structure, thermal properties and sintering resistance of YSZ

6-8 wt% yttria-stabilized zirconia (YSZ) has been widely employed as thermal barrier coating (TBC) to protect the high-temperature components of aero-engine and gas-turbine. However, the phase transition and sintering densification at high temperature seriously limit its application above 1200 °C. On account of this, CeO2 and Sc2O3 were doped into the YSZ by solid-state reaction sintering method in this paper. The effects of doping on the crystal structure, phase transition behavior and sintering resistance were investigated on the basis of XRD, Raman and FESEM, and the evolution of thermal properties of the ceramics was also analyzed. The results indicated that doped CeO2 increases the cell volume and tetragonal degree, but doped Sc2O3 was opposite. Co-doping caused not only significant difference in atomic mass and radius but also the formation of a large number of oxygen vacancies in the ceramics. Therefore, CeScYSZ showed the lowest thermal conductivity (1.53 W‧m−1‧K−1), which was about 23% lower than that of YSZ (2.00 W‧m−1‧K−1). More importantly, the oxygen vacancy also effectively stabilized the octet lattice, while the increase of lattice energy caused by Sc-O bond made it difficult for ions to misplace, which finally well prevented the transformation from t phase to m phase. There was no detrimental m-ZrO2 phase formation in the CeScYSZ after 120 h at 1500 °C. Besides, Co-doping could simultaneously overcome the poor sintering resistance caused by single CeO2 doping and the lower thermal expansion coefficient caused by single Sc2O3 doping, thus the CeScYSZ should be an ideal long-acting thermal protection material at higher temperatures.