Formation of Ultrafine Tetragonal ZrO₂ Powder Under Hydrothermal Conditions

Abstract

Ultrafine tetragonal ZrOz powder was prepared by hydrothermal treatment at 100 MPa of amorphous hydrous zirconia with distilled water and LiCl and KBr solutions. The resulting powder consisted of well-crystallized particles; at 2OO0C, the particle size was 16 nm and at 500°C, 30 nm. Under hydrothermal conditions tetragonal ZrOt appears to crystallize topotactically on nuclei in the amorphous hydrous zirconia.

Zirconia: A Review of a Super Ceramic

“…For example, Uvage at al. 53 attributed the t-Zr0 2 metastability to these structural similarities, while Tani et al 54 proposed a mechanism of "topotactic" crystallization of t-Zr0 2 on nuclei in the amorphous zirconia.…”

Transformation of Glassy Palladium‐Zirconium Alloys to Highly Active CO‐Oxidation Catalysts During In Situ Activation Studied by Thermoanalytical Methods and X‐Ray Diffraction

“…Livage et al [12] ascribe initial formation of the tetragonal phase to the structural similarity between the amorphous and tetragonal form of Zr02. Similarly, Tani et al [13] proposed a mechanism of topotactic crystallization of tetragonal zirconia on nuclei in the amorphous Zr02. Whether the palladium phases influence the stability of the tetragonal zirconia can not be answered from the present study and needs further investigation.…”

Electron microdiffraction studies of zirconia particles

“…If the crystallite size attains a critical value of 30 nm or above, the tetragonal--, monoclinic transformation is favoured. This theory was questioned by the data of Morgan [21] among others [22][23][24][25][26] who was able to produce 6 nm monoclinic zirconia particles by extensive refluxing of zirconyl chloride solution at pH 1-2. We reported earlier that the precipitation of zirconia at pH 2-4 from zirconyl chloride solution produced ultrafine tetragonal zirconia particles with X-ray crystallite size of about 15-16 nm in size after calcination at 500 ~ for 5 h. It was also reported that this tetragonal phase is transformed to monoclinic phase with increasing calcination time at 500 ~ [12].…”