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

BaLa2Ti3O10 (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 Basingle bondO layer in the BLT crystal.