Borohydride synthesis and stabilization of flake-like tetragonal zirconia nanocrystallites

Flake-like particles of tetragonal zirconia (t-ZrO(2)) were synthesized using ZrOCl(2 center dot)8H(2)O as zirconium precursor, and sodium borohydride (NaBH(4)) and cetyltrimethylammonium bromide (CTAB) as precipitating agent and surfactant, respectively. Small-sized nuclei, which formed during the borohydride synthesis, play an important role in the formation of small sized crystallites (5 nm) even at 600 degrees C and stabilization of t-ZrO(2) in both the samples synthesized with and without surfactant. In the sample synthesized without CTAB, a minor m-ZrO(2) phase (5 vol.%) along with the major t-ZrO(2) phase having a crystallite size of 20 nm, was observed at 700 degrees C. However, the use of surfactant leads to the formation of stabilized t-ZrO(2) nanoparticles with a smaller crystallite size of 15 nm. SEM micrographs of t-ZrO(2) show elliptical as well as elongated shaped flake-like morphology. The formation of small sized crystallites and slow growth of nucleation embryo play an important role in stabilizing the t-ZrO(2) up to as high temperature as 700 degrees C. (C) 2010 Elsevier B.V. All rights reserved.