This study deals with the deposition of coating materials that can be difficult to process by plasma spraying, including lanthanum and gadolinium zirconate, two pyrochlores of interest for thermal barrier applications, and lanthanum strontium cobalt ferrite (LSCF), a perovskite of interest for gas separation membranes. In addition to conventional atmospheric plasma spraying (APS), the feedstock powders were applied by suspension plasma spraying (SPS) and plasma spray-physical vapor deposition (PS-PVD). The spraying processes are described in detail along with the characteristics of the powders and coatings and the effects of various spray parameters on splat behavior and coating composition and structure.

The manufacture of submicrometer-structured coatings by thermal spraying is subjected nowadays to increasing research efforts in order to obtain unique and often enhanced properties compared to conventional coatings. Injecting suspensions of submicron ceramic particles into the plasma jet or the flame enables to deposit finely-structured coatings. Such fine microstructures can be advantageous for applications in the field of thermal barrier coatings (TBCs) for gas turbines. Often, suspension plasma sprayed (SPS) TBCs show unique mechanical, thermal and optical properties compared to conventional atmospheric plasma sprayed (APS) TBCs. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results show the capability of SPS to obtain yttria-stabilized zirconia (YSZ) coatings with high density of vertical segmentation cracks, yielding high strain tolerance and low Young’s modulus, while the porosity is still large compared to APS segmented coatings. Besides, sintering behavior of complete TBC systems under a thermal gradient exposure is of high importance. The evolution of the coating microstructure during thermal cycling test at very high temperature (1400°C) in our burner rigs as well as under isothermal annealing and its effects on the coating properties such as Young’s modulus were investigated.