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

• Substrate template effect on lattice structure of plasma sprayed 8YSZ was studied.
• 8YSZ splats were deposited on tetragonal (3YSZ) and cubic substrate (8YSZ) by APS.
• Splat TEM samples were processed by focus ion beam technique.
• Epitaxial grain growth on 8YSZ forms when the substrate is preheated to 800 °C.
• Epitaxial grain growth on 3YSZ forms as the substrate is preheated to 1200 °C.

The substrate template effect on the crystalline structure of plasma sprayed 8YSZ (8 mol%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. Focused ion beam (FIB) was utilized to prepare TEM cross-sectional sample of splats. The crystalline structures of both splats and the underlying substrates were examined by HR-TEM. Results show that the 8YSZ splats deposited on the polished sintered cubic structure 8YSZ substrate at a substrate surface temperature of 900 °C exhibit cubic lattice structure and the epitaxial grain growth was confirmed between the crystalline of splat grain and immediately underlying cubic crystalline substrate grain. Epitaxial grain growth is detected between the 8YSZ splat crystals and the 3YSZ 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.