Modelling the nature of disorder in talc by simulation of X-ray powder patterns

A sample of talc from Borgotaro (Parma, Italy) has been selected for its ph ase purity in order to investigate the nature of layer stacking disorder in talc. Earlier models describing disorder in talc have been fully revised u sing simulated powder patterns generated by DIFFaX. A new model has been su ggested consisting of a random sequence of layers, stacked by a/3 along one of the pseudohexagonal X directions, affected by random planar disorder wi th components of +/-b/3. Modelling the planar disorder effects does not suf fice alone to perfectly reproduce the experimental powder pattern, and othe r microstructure effects such as preferred orientation and size of the cohe rent crystallite domains must also be considered.