Y3Ce7Ta2O23.5 and Yb3Ce7Ta2O23.5—Two kinds of novel ceramics for thermal barrier coatings

Abstract

For the development of ceramic candidates for thermal barrier coatings, two kinds of new ceramics, Y3Ce7Ta2O23.5 and Yb3Ce7Ta2O23.5, were synthesized by sintering at 1873 K for 10 h. The obtained samples were composed of a single fluorite-type phase, and their relative densities are greater than 90%. Because of phonon scattering caused by the complex lattice, the large number of oxygen vacancies, and substituted atoms, the thermal conductivity is lower than that of 8YSZ. The coefficients of thermal expansion (CTEs) of these two products are located in the range of 10.22–12.57 × 10−6/K and 9.62–12.66 × 10−6/K, respectively, from 323 K to 1473 K, and they also exhibit excellent phase stability up to 1473 K. However, their thermal conductivities and CTEs are lower than those of RE2Ce2O7 (RE = La, Nd, or Sm).