The study of phase stability and thermal shock resistance of a Scandia-Ceria stabilized zirconia as a new TBC material

The nanostructured Scandia-Ceria stabilized Zirconia (SCSZ) was synthesized via a sol-gel route and the effects of different contents of Scandia stabilizer (3.6-8 mol. %) on phase stability and thermal shock resistance were investigated compared to traditional YSZ. The results revealed that after heat treating at 1400 degrees C for 25 h, the optimum structure belonged to 4.78SCSZ system due to non-formation of monoclinic and cubic phases in structure and high tetragonal (t') phase stability. The increased coefficient of thermal expansion of 4.78SCSZ was also confirming the decreased thermal mismatch stresses and improvement in thermal performance compared to traditional YSZs. In this regard, the results of thermal shock resistance showed a promising cyclic lifetime. However, the microstructural investigations indicated that the TGO layer has been formed during thermal treatment and hence, the combined effects of TGO growth and thermal expansion misfit have intensified tensile stresses governing crack growth near and parallel to coating interface.