Splat morphology and microstructure of chelate flame sprayed Er₂O₃ films

Abstract

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.