Optimization thermophysical properties of TiO2 alloying Sm3TaO7 ceramics as promising thermal barrier coatings

TiO2 alloying effect is applied to optimize the thermophysical properties of fluorite-type Sm3TaO7 ceramics synthesized via solid-state reaction, and the influence of TiO2 alloying effect on the optical properties and elastic modulus is determined. According to the decreasing unit cell volume calculated by the X-ray diffraction and the broadening Raman peak, Ti4+ substitutes the same number of Sm3+ and Ta5+ ions of Sm3TaO7 ceramics at the same time. As Ti4+ substitutes Sm3+ and Ta5+ ions, the band gap of TiO2-Sm3TaO7 ceramics decreases from 4.71 to 4.11 eV. The phase transition of Sm3TaO7 ceramics is eliminated by TiO2 alloying effect and the coefficient of thermal expansion is increased. Via TiO2 alloying effect, two different phonon scattering mechanisms: (a) the misfit of atomic weight and ionic radius among Ti4+, Sm3+, and Ta5+ ions; (b) the rattling Ti4+ ions are introduced in Sm3TaO7 ceramics. The lowest thermal conductivity of TiO2-Sm3TaO7 ceramics reaches 1.37 W K-1 m(-1) (800 degrees C, 9 mol% TiO2-Sm3TaO7), which is much lower than 7YSZ and Sm2Zr2O7 ceramics. Accordingly, it is believed that TiO2-Sm3TaO7 ceramics are promising thermal barrier coatings.