Ruddlesden–Popper structured BaLa2Ti3O10, a highly anisotropic material for thermal barrier coatings

Abstract BaLa 2 Ti 3 O 10 (BLT) with Ruddlesden–Popper structure is investigated as a material for thermal barrier coatings (TBCs). BLT shows excellent sintering resistance and remains phase stability at 1500 °C for 110 h. After annealing at 1500 °C for 1 h, BLT bulk material exhibits c -axis textured structure with c -axis parallel to the hot pressing direction. Thermal expansion coefficients of BLT in a – b plane are in the range of 9.5 × 10 −6 –11.3 × 10 −6 K −1 , whereas those along c -axis range from 10.4 × 10 −6 to 12.1 × 10 −6 K −1 , which are comparable to those of 8YSZ. The thermal conductivities of BLT in a – b plane and along c -axis are 1.41–1.71 and 1.31–1.60 W/mK, respectively, nearly 20% lower than those of 8YSZ. The anisotropy in thermo-physical properties is attributed to the insertion of weakly bonded Ba O layer in the BLT crystal.