Synthesis and characterization of $Y_3Al_5O_{12}$ and $ZrO_2–Y_2O_3$ thermal barrier coatings by combustion spray pyrolysis

$Y_3Al_5O_{12}$ and $ZrO_2–Y_2O_3$ (8 mol% YSZ) coatings for potential application as thermal barrier coatings were prepared by combustion spray pyrolysis. Thermal cycling of as deposited coatings on stainless steel and FeCrAlY bond coat substrates was carried out at $1000^oC$ and $1200^oC$ to determine the thermal fatigue response. Structural and morphological studies on $Y_3Al_5O_{12}$ and 8 mol% YSZ coatings before and after thermal cycling have been carried out. It has been noted that the coatings on FeCrAlY substrates remain intact after 50 cycles between room temperature and $1200^oC$, whereas the coatings on stainless steel show some minor damage such as peeling off near the periphery after 50 cycles at $1000^oC$.Thermal diffusivity values of $Y_3Al_5O_{12}$ and 8 mol% YSZ films were measured by using photo thermal deflection spectroscopy and the values are lower than those of coatings produced by conventional techniques such as EBPVD and APS