Improved Toughness and Thermal Expansion of Non-stoichiometry Gd2 − xZr2 + xO7 + x/2 Ceramics for Thermal Barrier Coating Application

Gd2Zr2O7 has been considered as a promising thermal barrier coating candidate, but its toughness and thermal expansion coefficient (TEC) need to be improved. In this study, Gd2 − xZr2 + xO7 + x/2 (x = 0, 0.1, 0.3, 0.5, 0.7) compounds were produced to improve the toughness and enlarge the TEC. Gd2Zr2O7 and Gd1.9Zr2.1O7.05 exhibited pyrochlore structure, while Gd2 − xZr2 + xO7 + x/2 (x = 0.3, 0.5, 0.7) consisted of pyrochlore and t'-ZrO2 phases. With increasing ZrO2 content, the pyrochlore in the compounds had decreased lattice parameter, and its ordering degree decreased when x ≤ 0.3, then it almost kept unchanged with higher ZrO2 content. Among the Gd2 − xZr2 + xO7 + x/2 ceramics investigated, the toughness of the compounds increased with increasing ZrO2 content, while Gd1.7Zr2.3O7.15 exhibited the largest TEC. The related mechanisms were discussed in detail.