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 degreesC. Prolonged heat treatment at 900 degreesC showed that Li2ZrO3 pellets were stable at this temperature for up to 3 h. For longer heat treatments at 900 degreesC, 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 degreesC produced a 170 mum 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 mol(-1). (C) 2003 Elsevier Ltd. All rights reserved.