Enhanced BaZrO3 mechanosynthesis by the use of metastable ZrO2 precursors

Abstract

The current work assesses the impact of structural differences between stable and metastable ZrO₂ precursors on the mechanochemical preparation of BaZrO₃. Monoclinic (m-ZrO₂) and tetragonal (t-ZrO₂) zirconia polymorphs were prepared without stabilizing additives by slow alkaline precipitation. High-energy milling of the individual ZrO₂ precursors induced different partial transformations in each case. The as-synthesized m-ZrO₂ powders showed partial conversion to the tetragonal polymorph on mechanical activation, reaching about 10% t-ZrO₂ after 420 min accompanied by increases in strain. In contrast, the as synthesized t-ZrO₂ powders underwent the inverse transformation to the monoclinic phase, producing about 50% m-ZrO₂ after 120 min with the liberation of strain. The t-ZrO₂ 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 BaZrO₃ has been discussed with respect to the differing behaviour of the ZrO₂ precursors upon mechanical activation and associated thermodynamic perspectives.