Thermal aging behavior of plasma sprayed LaMgAl11O19 thermal barrier coating

The crystallization behavior of the amorphous phase of the plasma sprayed LaMgAl11O19 (LaMA) coating during thermal aging processes has been investigated. Results indicate that LaMA coating exhibits much similar microstructure and thermal properties such as close coefficient of thermal expansion and specific heat capacity etc. to the sintered LaMA bulk after aging at 1673 K for 20 h. On the other hand, a solid state reaction seems to occur to reform the ideal magnetoplumbite-type LaMA phase coupled with the formations of the La-rich aluminate intermediate phases. When the aging temperature is held between 1273 K and 1473 K, nanosized platelet-like grains as well as sub-grains with high aspect ratios are present. The phase stability has been investigated through the chemical compositions and X-ray diffraction analysis. The recrystallization mechanism of the amorphous LaMA coating has been explored by tracing the microstructure evolutions during thermal aging process.