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

Abstract

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.

Keywords:

• HRTEM
• silicate
• stacking faults
• image simulation

Acknowledgements

Thanks are due to Dr Paul Trusty and Dr Clive B. Ponton for the provision of hot-pressed Y₂Si₂O₇ specimens and to Maria Sycha for preparing TEM specimens from the ceramic. Helpful discussions with Professor H. Fuess, Dr Thomas Weirich and Dr G. Miehe are gratefully acknowledged. This work would have been impossible without the provision of laboratory facilities (specifically access to high-specification transmission electron microscopes) by Professor Manfred Rühle and Professor Hartmut Fuess. IM is indebted to the Alexander von Humboldt foundation for a research fellowship at the MPI in Stuttgart.

Notes

^†Formerly at Institut für Materialwissenschaft, TU-Darmstadt, Petersenstr. 23 D-64287 Darmstadt, Germany and Max-Planck-Institut für Metallforschung, Heisenberg St. 5, D-70569 Stuttgart, Germany, where large portions of the work reported in this paper were carried out.

Additional information

Notes on contributors

I. MacLaren†

†Formerly at Institut für Materialwissenschaft, TU-Darmstadt, Petersenstr. 23 D-64287 Darmstadt, Germany and Max-Planck-Institut für Metallforschung, Heisenberg St. 5, D-70569 Stuttgart, Germany, where large portions of the work reported in this paper were carried out.