Effect of NaF content on the preparation of zirconia whiskers by molten salt method

Abstract

Zirconia whiskers were successfully fabricated by molten salt method, using NaVO3/NaF as composite molten salt. The effect of NaF content on the growth of zirconia whiskers were systematically investigated by XRD, FE-SEM, TEM, SAED, HR-TEM, Raman and XPS. When optimized NaF content is 10%, the obtained zirconia whiskers with monoclinic crystal structure show an length of 1–3 μm and diameters of 100–300 nm. The as-prepared whiskers preferentially grow along [001] direction and exhibit a smooth surface without distinct defects. Fluoride is proved to play an important role in the growth of zirconia whiskers. On the one hand, fluoride can be served as mass transfer agent, promoting the dissolution and precipitation of ZrO2 through the mass transfer process of fluorozirconate species. On the other hand, fluoride can act as morphology controlling agent, enhancing the anisotropic growth of ZrO2 crystals by the formation of fluorine-terminated surface.