The microstructure of ceramic-based composite coatings for thermal barrier (A1₃O₃-FNA₁-Cu) has been studied by SEM and X-raying. The particular attention has been paid to the diffusion reaction,liqued sintering and the small grain size of the coatings by flame spraying ceramic-based composite powders. The effect of these microstructure features on the bond strength,heat ressistivity and spalling resistance of the coating is discussed also.