Simple preparation of yttria-stabilized zirconia powders by plasma discharge electrolysis in nitrate solution

Yttria-stabilized zirconia (YSZ) powder is widely used in battery and thermal barrier coatings. This article reports a method of preparing YSZ powder using plasma in air atmosphere at room temperature in 0.34 M ZrO (NO${}_3$)${}_2$ - 0.06 M Y(NO${}_3$)${}_3$ solution. Diverse characterization techniques are utilized to examine the morphology and composition of synthesized powders. Electrolytic green powder consists mainly of hydroxide, which is annealed to form a well-crystallized YSZ oxide powder with coexisting tetragonal and cubic phases. The green powder is composed of micrometer-sized particles, with a particle size distribution (D${}_{50}$) of 51.90 µm. The molar ratio of Y to Zr is 2.84:1. The YSZ powder is finer (D${}_{50}$ is 5.80 µm) with irregular nanoparticles aggregating together, and the molar ratio of Y to Zr is 2.57:1. Hydroxyl radicals (OH·) and hydrogen radicals (H·) are found in the flame during discharge electrolysis, and the main formation reactions of the powders by this process are H${}_2$O + 2e${}^{-}$ → H${}_2\uparrow$ + 2OH${}^{-}$; Zr${}^{4+}$ + 4OH${}^{-}$ + nH${}_2$O → Zr(OH)${}_4$·nH${}_2$O$\downarrow$; and Y${}^{3+}$ + 3OH${}^{-}$ + nH${}_2$O → Y(OH)${}_3$·nH${}_2$O$\downarrow$. The conductivity of electrolyte sintered by YSZ powders increases with rising temperature, reaching 0.038S cm${}^{-1}$ at 1000 °C. (© 2024 Wiley‐VCH GmbH)