Enhanced BaZrO3 mechanosynthesis by the use of metastable ZrO2 precursors

• Published in: Dalton transactions : an international journal of inorganic chemistry 2014-06, Vol.43 (24), p.9324-9333
• Main Authors: Sherafat, Z, Antunes, I, Almeida, C, Frade, J. R, Paydar, M. H, Mather, G. C, Fagg, D. P
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c4dt00683f

The current work assesses the impact of structural differences between stable and metastable ZrO 2 precursors on the mechanochemical preparation of BaZrO 3 . Monoclinic (m-ZrO 2 ) and tetragonal (t-ZrO 2 ) zirconia polymorphs were prepared without stabilizing additives by slow alkaline precipitation. High-energy milling of the individual ZrO 2 precursors induced different partial transformations in each case. The as-synthesized m-ZrO 2 powders showed partial conversion to the tetragonal polymorph on mechanical activation, reaching about 10% t-ZrO 2 after 420 min accompanied by increases in strain. In contrast, the as synthesized t-ZrO 2 powders underwent the inverse transformation to the monoclinic phase, producing about 50% m-ZrO 2 after 120 min with the liberation of strain. The t-ZrO 2 precursor was shown to exhibit the higher reactivity with barium peroxide, yielding significantly earlier formation of barium zirconate under room-temperature mechanosynthesis. The progress of the mechanochemical formation of BaZrO 3 has been discussed with respect to the differing behaviour of the ZrO 2 precursors upon mechanical activation and associated thermodynamic perspectives. Enhanced mechanochemical preparation of BaZrO 3 can be achieved upon milling mixtures of barium peroxide with metastable tetragonal ZrO 2 precursors.