Effect of Yb, Fe and Mo, Ti Co-doping on thermal and mechanical properties of Gd2Zr2O7 ceramics

The utilization of Gd2Zr2O7 (GZO)-based ceramics in thermal barrier coatings (TBCs) has been expanding due to their advantageous properties. However, issues such as limited fracture toughness, dependence on rare-earth elements, and high production costs present challenges for sustainability. In this study, GZO ceramics were co-doped with varying levels of non-rare-earth elements, specifically Fe, Mo, and Ti, to investigate their mechanical and thermophysical characteristics. The results revealed that co-doping led to a slight reduction in mechanical properties and the thermal expansion coefficient while significantly enhancing thermal conductivity through the reduction of Gd2O3 content in GZO ceramics. The thermal conductivity of undoped GZO at 900 degrees C was measured at 2.21 W.m- 1.K- 1, whereas the lowest thermal conductivity observed in co-doped GZO was 0.889 W.m- 1.K- 1. At 1150 degrees C, the thermal expansion coefficient of undoped GZO was determined to be 11.48 x 10- 6.K- 1, while co-doped GZO ceramics exhibited values in the range of 10.45-11.27 x 10- 6.K- 1. In terms of mechanical properties, the hardness of undoped GZO was 10.88 GPa, whereas co-doped ceramics exhibited hardness values ranging from 10.73 to 10.12 GPa. The elastic modulus of undoped GZO was measured at 307 GPa, while co-doped samples demonstrated values between 302 and 330 GPa. Additionally, the fracture toughness of undoped GZO was calculated as 1.36 MPa m1/2, while co-doped ceramics exhibited values between 1.34 and 0.92 MPa m1/2. Based on these findings, co-doped GZO ceramics demonstrate potential for TBC applications. Furthermore, reducing the reliance on rare-earth elements in these ceramics could contribute to the development of more sustainable and environmentally friendly coating materials.