Effect of slurry solid content and sintering temperature on dielectric breakdown strength in nanostructured alumina coatings during feedstock powder preparation

In this study, the effects of slurry solid content and sintering temperature of the reconstituted nano-Al₂O₃feedstock powder on the phase composition, microstructure, and breakdown strength of the deposited coatings were investigated. The results indicate that the slurry solid content primarily influences the morphology of the feedstock powders, whereas the sintering temperature affects the phase composition and grain size. The phase structure of the as-sprayed coatings was composed of α-Al₂O₃and γ-Al₂O₃, regardless of whether the phase of the feedstock powder used was composed of θ and α phases or pure α phase. The highest dielectric breakdown strength of 10.32 ± 0.56 kV/mm was achieved when the feedstock powder preparation parameters were set at a slurry solid content of 60 wt% and a sintering temperature of 1100 °C. A simplified model was proposed to describe the relationship between the dielectric breakdown strength of the deposited coating and the α phase and porosity. The dielectric breakdown strength of the deposited coatings is approximately proportional to the α phase content and inversely proportional to the porosity.