Structure and possible origins of stacking faults in gamma-yttrium disilicate

Parallel stacking faults on (010) planes are frequently observed in hot-pressed Y2Si2O7. A combination of conventional dark-field imaging and high-resolution transmission electron microscopy was used to investigate the structure of these faults. It was found that they consisted of the repeat of one layer of the two-layer γ-Y2Si2O7 structure with an associated in-plane rigid body displacement. The resulting structure was confirmed by image simulation of high-resolution images from two perpendicular projections. A model for the formation of the stacking faults is proposed as a consequence of a transformation from β-Y2Si2O7 to γ-Y2Si2O7 in the hot pressing.