Investigation of the effects of calcination temperature on the structure of LaMgAl11O19 for thermal barrier coating applications

Yttria Stabilized Zirconia (YSZ) is the most common thermal barrier coating material with a temperature tolerance up to 1200°C above which it undergoes phase transitions deteriorating its thermo-mechanical properties. Apart from YSZ, oxides having the complex Magnetoplumbite structure such as LaMgAl₁₁O₁₉ are potential candidates for even higher temperature applications due to their thermo-physical properties. In this work, LaMgAl₁₁O₁₉ was synthesized through sol-gel citric acid method using nitrate precursors. The powders were subjected to calcination treatment for 5 hours at 1000 °C, 1100 °C, 1200 °C, 1300 °C and 1400 °C. The microstructure was analyzed by XRD and SEM techniques. XRD results identified a pure single phase of LaMgAl₁₁O₁₉, obtained successfully at 1200 °C. Effects arising from changing calcination temperature show that lattice strain reduced and crystallite size increased with increase in temperature. SEM results revealed that the platelet structure of LaMgAl₁₁O₁₉ was obtained which could increase thermal tolerance.