Splat morphology and microstructure of chelate flame sprayed Er<sub>2</sub>O<sub>3</sub> films

The chelate flame spray (CFS) method is an inexpensive flame spray technique with low energy consumption used to deposit metal oxide (M2O3) films using M-ethylenediaminetetraacetic acid (EDTA·M·H) complexes. In this study, EDTA·Er·H was used as the raw material to investigate the cross-sectional structures of the Er2O3 films, and substrates with different common materials, i.e., quartz glass, stainless steel (304), and aluminum-magnesium alloy (A5052), were selected. We found that in the CFS deposition process, EDTA·Er·H was decomposed, oxidized and melted in the flame to form molten Er2O3 particles, and Er2O3 films with an average thickness of 9.7–13.5 µm, cross-sectional porosity of 1.6–4.9 %, and crack numbers of 29–51 were deposited on quartz glass. Oxide films with 7.6–14.3 µm thickness were synthesized on an aluminum-magnesium alloy (A5052) substrate. The cross-sectional porosity and microcrack numbers of these films were 5.2–6.9 % and 10–20, respectively. In addition, to observe the Er2O3 film stacking structure more clearly, we screened the powder raw materials to make them uniform. The results of this study enable the design of a ceramic film microstructure that reduces cracks in the ceramic film, thereby increasing the application potential.