Microstructure and mechanical properties of Sc2O3-Y2O3 co-doped ZrO2 ceramic materials for thermal barrier coating

Partially stabilized zirconia （7YSZ） with a mass fraction of 7±1% yttrium oxide is a widely used ceramic material for thermal barrier coatings. However， its phase stability， sintering resistance， and mechanical properties decreased during the long-time operation above 1200 ℃. A new type of Sc2O3-Y2O3 co-doped ZrO2 thermal barrier coating ceramic material was proposed ， and a molar fraction of 7.5%Sc2O3-x%Y2O3-（92.5-x）%ZrO2（x=0，0.1，0.2，0.3） ceramics were prepared by solid-state reaction method. The effects of Y2O3 doping on the microstructural， phase evolution， and mechanical properties（including Vickers hardness， fracture toughness， elastic modulus and three-point bending strength）were explored by XRD， SEM， and other testing methods. The results show that the relative density of Sc2O3-Y2O3 doped ZrO2 ceramics sintered at 1450 °C for 3.5 h is more than 97%， and the phase structure is composed of tetragonal phase. Compared with 6-8YSZ ceramics， Sc2O3-Y2O3 doped ZrO2 ceramics exhibit similar Vickers hardness （13-14 GPa）， fracture toughness （6.5-7.0 MPa·m1/2）， elastic modulus （211-214 GPa）and three-point bending strength（520-850 MPa）. Fracture mechanism shows a mixture of transgranular and intergranular fracture modes， in which transgranular fracture is dominant.This ceramic can be explored as a potential thermal barrier coating material for high-temperature applications.