Characterization of atmospheric plasma-sprayed Sc₂O₃-ZrO₂ electrolyte coating

Sc₂O₃ stabilized ZrO₂ (ScSZ) coating in free standing planar shape was prepared by atmospheric plasma spraying (APS) using ScSZ powder consisting of 10 mol% Sc₂O₃. ScSZ powder was prepared by solid phase reaction followed by sintering and screening processes. The coating microstructure was characterized using X-ray diffraction and scanning electron microscopy. The electrical conductivity of ScSZ coating was measured using both DC and AC approaches. The electrical conductivity of the as-sprayed ScSZ coating was about 0.07 S/cm at 1000 °C. It is one-fourth that of the sintered one. This result is due to the lamellar structure feature with the limited interface bonding which dominates the electrical conductivity of APS coatings. The activation energy of the as-sprayed coating was 1.31 eV at temperature range less than 750 °C and 0.97 eV at above 750 °C. The change of activation energy indicates that the ion transportation dominants are changed with temperature. This fact is due to higher activation energy of the grain boundary than that of intragrain.