Effect of Phase Structure Evolution on Thermal Expansion and Toughness of (Nd1-xScx)2Zr2O7 (x = 0, 0.025, 0.05, 0.075, 0.1) Ceramics

Nd2Zr2O7 is being explored as an alternate thermal barrier coating (TBC) material for operating above 1300 °C, and great effort has been made to enlarge its thermal expansion coefficient (TEC) and improve its toughness. In this study, Sc2O3 was doped to Nd2Zr2O7. The phase structure, TECs and toughness of (Nd1-xScx)2Zr2O7 (x = 0, 0.025, 0.05, 0.075, 0.1) compounds were investigated. (Nd1-xScx)2Zr2O7 (x = 0, 0.025, 0.05, 0.075) exhibited pyrochlore structure, while (Nd0.9Sc0.1)2Zr2O7 consisted of pyrochlore and fluorite phases. With the increase of the Sc2O3 content, the ordering degree of the pyrochlore in the compounds decreased. In (Nd1-xScx)2Zr2O7 series, (Nd0.925Sc0.075)2Zr2O7 exhibited the largest TEC, while the toughness of the compounds increased with increasing the Sc2O3 content. The related mechanisms were discussed based on the crystal structure analysis. Considering the TEC and toughness, 10 mol% Sc2O3 was suggested as the optimal doping content for Nd2Zr2O7 ceramic.