Reaction mechanisms and kinetics of the synthesis and decomposition of lithium metazirconate through solid-state reaction

The reaction mechanisms and kinetics describing the formation and surface decomposition of lithium metazirconate pellets (Li2ZrO3) have been investigated during Li2ZrO3 formation via solid-state reaction. Samples were analysed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A metastable tetragonal Li2ZrO3 phase was synthesised at low temperatures, recrystallizing into a monoclinic structure when the temperature was increased above 800 °C. Prolonged heat treatment at 900 °C showed that Li2ZrO3 pellets were stable at this temperature for up to 3 h. For longer heat treatments at 900 °C, Li2ZrO3 lost Li2O from the surface of the pellets, decomposing to ZrO2. Similar, more rapid, decomposition behaviour was found at higher temperatures. Pellets heated for 48 h at 1100 °C produced a 170 μm thick ZrO2 layer on the surface of the pellets. Modelling the loss of lithium oxide from Li2ZrO3 in terms of a diffusion-controlled model, the activation energy for this decomposition of Li2ZrO3 to ZrO2 was estimated to be 210 kJ mol−1.