The synthesis of thermochemically stable single phase lanthanum titanium aluminium oxide

Abstract Lanthanum titanium aluminium oxide (LaTi2Al9O19, LTA) synthesized by solid state reaction has been proven to be a promising thermal barrier material. However, LTA synthesized via solid state reaction requires a high processing temperature of at least 1500 °C for 24 h. In this paper, single phase LTA was synthesized by sol–gel at a lower temperature (1350 °C) and the process parameters, phase composition, and relative thermal properties were investigated. Two-step calcination was used to obtain fine LTA powders. According to X-ray diffraction, the best calcination temperature of sol–gel synthesized LTA is 1350 °C. XRD results also showed the thermochemical stability of sol–gel synthesized LTA, which does not react with Al2O3 up to 1500 °C, to be excellent. Compared to LTA synthesized by solid state reaction, sol–gel synthesized LTA has higher coefficients of thermal expansion (CTEs) which are circa 10.2×10−6 °C−1 at 950 °C, related to the size dependent characteristic of CTEs. Therefore, sol–gel synthesized LTA can be a promising candidate as a thermal barrier material on Ni-based superalloys.