WEB Microstructural and chemical characteristics of flame sprayed (Bi0.5Na0.5)TiO3 coatings using different fuel/oxygen ratioFriday (28.02.2020) 04:04 - 04:04 Poster Room Part of:
(Bi0.5Na0.5)TiO3 (BNT) has been widely studied due to its promising properties for the substitution of PZT-based piezoceramics. The development of electronic devices technology has raised interest in the production of ferroelectric and piezoelectric components with scalable processes. The fabrication of piezoceramic coatings by thermal spray has been recently explored. These materials with perovskite structure have been deposited as thick coatings. However, the ferroelectric and piezoelectric responses are commonly achieved with post heat treatment. The volatility of elements at high temperatures and the formation of secondary and amorphous phases are still a concern. This study focuses on the fabrication and evaluation of BNT coatings deposited using a low-cost and -energy consumption flame spray (FS) process. FS produces low flame temperature and velocity of the in-flight particles during deposition compared to plasma techniques. Spray-dried spherical-shaped and rhombohedral BNT powder were used as feeding material. BNT coatings were deposited by FS varying the fuel-oxygen ratio (F/O) in the fuel-rich, stoichiometric and oxidizing flame regimes keeping constant the total flow of combustion mixture, stand-off distance, and powder feed rate. Structural, microstructural and chemical characteristics were analyzed by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy (EDS), respectively. Coatings cross section showed typical thermal sprayed microstructure consisting of molten and semi-molten particles, cracks, and porosity. All deposited coatings presented a major BNT crystalline phase. However, a fraction of a phase in an amorphous state was also observed, with variable content depending on each condition. For instance, the amorphous phase was higher in the coatings deposited with stoichiometric flame, followed by the fuel-rich and then the oxidizing conditions. This is probably caused by the flame temperature associated to the F/O ratio, which the highest in the stoichiometric condition. The high temperature leads to rapid quenching of the molten state preventing full recrystallization of the BNT structure. Additionally, anatase and rutile phases were observed in all coatings and their content increased with higher F/O ratios. EDS analysis evidenced Bi loss in the three conditions respect to the feeding powder being the oxygen-rich condition the one with the lowest effect.
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|Poster||Submission 339_abstract MSE 2020||Microstructural and chemical characteristics of flame sprayed (Bi0.5Na0.5)TiO3 coatings using different fuel/oxygen ratio||239 KB||Download|