Stabilization of ZrO2 PVD coatings with Gd2O3

Zirconia coatings partially or fully stabilized have several high temperature applications (e.g. turbine blades and diesel engines parts). However, to increase the thermodynamic efficiency of these systems and reduce their thermal conductivity new kind of stabilizers are required. Gd2O3, among other rare earth oxides, is a potential candidate as a dopant or as a constituent together with the ZrO2Y2O3 system. The aim of the present paper is to study the influence of the Gd2O3 in the high-temperature phase stability of zirconia. Thin films of ZrO2Gd2O3 and ZrO2Y2O3Gd2O3 have been deposited by reactive DC magnetron sputtering with different dopant percentages and a wide range of techniques have been used for their characterization. X-ray diffraction (XRD) was used for the structural characterization of the coatings, to study the influence of Gd2O3 addition on the high-temperature stabilized phases, and its influence on the microstructure and the level of stress. Energy dispersive X-ray spectroscopy (EDX) was used to assess the coating composition. The mol% of Gd2O3 determined in the coatings is in the range of 2.1 to 17.5. The transition from the tetragonal to the cubic phase was clearly observed in the range of 5 to 6.5 mol% of dopant. Scanning electron microscopy (SEM) was used to determine the film thickness, to study the microstructure of the film in cross section and also the surface morphology. The surface microtopography was analyzed by atomic force microscopy (AFM) and nondestructive laser microtopography. The roughness of the coatings was evaluated and correlated with the optical parameters obtained by optical spectroscopy. A detailed description of the results and their discussion will be presented in the paper.