Growth of Monoclinic ZrO 2 Thin, Flaky Crystals by Hydrothermal Decomposition of Zirconium Oxide Sulfate Crystals

Thin platelike hexagonal crystals of zirconium oxide sulfate (ZOS) with a chemical composition of Zr 3 O 5 SO 4 . n H 2 O were previously synthesized by the hydrolysis of an aqueous solution of 2 mol/L ZrOSO 4 at 240°C. The ZOS particles obtained were hydrothermally treated again in dilute sulfuric acid solution (<0.15 mol/L) at 240°C. The decomposition of ZOS and the nucleation and growth morphology of the monoclinic ZrO 2 crystals were automatically controlled with increasing sulfuric acid released by the decomposition of ZOS, and were influenced by the morphology of ZOS as precursors. Anisotropic monoclinic ZrO 2 single crystals, elongated thin and flaky particles (length: >2 (Am; width: about 0.1 μm; thickness:«0.01 μm), could be obtained under some conditions without the coexistence of another type of anisotropic ZrO 2 fibrous twin crystal.