Epitaxial grain growth during 8YSZ splat formation on polycrystalline YSZ substrates by plasma spraying

The effect of substrate template effect on the crystalline structure of plasma sprayed 8YSZ (8mol%Y₂O₃) splats was investigated by high resolution transmission electron microscopy (HR-TEM) examination of FIB-processed splat samples. 8YSZ splats were deposited by the atmospheric plasma spraying (APS) on the polished sintered tetragonal structure substrate (3YSZ) and cubic structure substrate (8YSZ) at different preheating temperatures. The focused ion beam (FIB) was utilized to prepared TEM cross-sectional sample of splats. The crystalline structures of both the splat and the underlying substrate were examined by HRTEM. Results showed that the 8YSZ splats deposited on the polished sintered cubic structure 8YSZ substrate at a substrate surface temperature of 900°C exhibited cubic structure and the epitaxial grain growth was confirmed between the crystalline of splat grain and immediately underlying cubic crystalline substrate grain. Moreover, epitaxial grain growth was confirmed between the crystalline of splat grain and the tetragonal structure substrate when substrate surface temperature was increased to 1200°C. The present results suggest that the crystalline structure formation of 8YSZ splats produced by plasma spraying was affected by the substrate template effect.