Monolithic t‐ZrO₂ Nanopowder through a ZrO(OH)₂·xH₂O Polymer Precursor

Abstract

Monolithic t‐ZrO2 (tetragonal structure) nanopowder is synthesized with an amorphous ZrO(OH)2·xH2O polymer precursor. The H2O molecules impart the structure and promote reconstructive thermal decomposition of the structure to t‐ZrO2 nanoparticles on heating at temperatures as low as 200°C. A prevalent endothermic heat output in the dissociation process controls the local temperature in exothermic nucleation and growth of various groups of the reaction species so that it is self‐controlled in high‐energy nanoparticles. Crystallites are, on average, d= 8 nm diameter, and they have a high value of Gibbs free energy or lattice volume Vo= 0.06770 nm3. The excess volume decreases to Vo= 0.06705 nm3 if the reaction temperature is increased to >200°C, i.e., approximately the bulk value of 0.06681 nm3; there is a minor increase to d= 12 nm at 600°C. Many oxygen vacancies in the thin surface space‐charge layers seem to support the stability of small particles in this particular polymorph. A pure m‐ZrO2 (monoclinic structure) appears with d= 22 nm at temperature as low as 800°C. The results are analyzed using X‐ray diffractometry, microstructure, infrared spectroscopy, and thermal studies of the polymer precursor and derivative t‐ZrO2 nanoparticles.

Sol-Gel Synthesis of Non-Silica Monolithic Materials

“…Recently, hierarchical zirconia monoliths were successfully synthesized using ZrCl 4 [89] and ZrOCl 2 [90,91] as precursors. ZrO(OH) 2 ⋅xH 2 O gels were made by drop-wise addition of ammonia into cooled aqueous solutions of ZrOCl 2 ⋅8H 2 O [90,91].…”

“…ZrO(OH) 2 ⋅xH 2 O gels were made by drop-wise addition of ammonia into cooled aqueous solutions of ZrOCl 2 ⋅8H 2 O [90,91]. The crystalline zirconia phase depended on the calcination temperature.…”

Synthesis of ZrMo2O8 polymorphs by a melt quenching method and mechanochemical activation

“…The absorption band at 580 cm −1 is characteristic of stretching vibrations of OMo 3 units formed by edge shared MoO 6 octahedra [49]. The absorption bands at 740, 520, 450 and 420 cm −1 are characteristic bands of ZrO 7 polyhedra building ZrO 2 oxide [50,51]. The spectra are drastically transformed after heat-treatment.…”

Synthesis of Lithium-doped Zirconia Nanoceramics of Controlled Oxygen Vacancies

“…In comparison to = 6.10 g/cm 3 in monolithic t-ZrO 2 14 , a smaller -value observed in this example is according to smaller ionic size of Li + relative to the Zr 4+ value. As can be analysed by intensities in the diffraction peaks, as described earlier [10][11][12] , the sample has a small impurity ~ 5 per cent due to incipient growth of m-ZrO 2 .…”

“…10 . Washing in cold water separated byproduct chlorides, resulting in a colorless transparent hydroxyl gel, which was then dried at 90-100 °C over a sand bath (Fig.…”