Non-equilibrium microstructure of bone china

Commercial bone china microstructures ale far from equilibrium consisting o f distinct legions of lath-like (0.4-10 mu m) anorthite and spheroidal (1-3 mu m) p-tricalcium phosphate (beta-TCP) nodules embedded in a heterogeneou s composition glass along with isolated irregular (less than or equal to 30 mu m) alpha-quartz crystals. The composition and morphology of the phases formed on firing suggest that anorthite crystallised in clay relicts by the reaction of metakaolin with CaO, beta-TCP crystallised from decomposition of bone ash, and that the liquid formed on vitrification has variable compo sition depending on the composition of adjacent phases. P2O5 was never dete cted in the glass suggesting that any P2O5 that dissolves in the liquid on firing is transient. The cracks sometimes observed in and around beta-TCP c lusters al ise fi om thermal expansion mismatch between beta-TCP and the su rrounding glass and anorthite. (C) 2000 IoM Communications Ltd.