Lattice defects in lawsonite: a TEM investigation
| Autor: | J. C. Doukhan, Fernando Cámara, Michael A. Carpenter |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Phase transition
Materials science 010504 meteorology & atmospheric sciences Lawsonite Condensed matter physics Precipitation (chemistry) 010502 geochemistry & geophysics 01 natural sciences Crystallography Geochemistry and Petrology Transmission electron microscopy Irradiation Texture (crystalline) Crystal twinning Beam (structure) 0105 earth and related environmental sciences |
| Zdroj: | Mineralogical Magazine. 65:33-39 |
| ISSN: | 1471-8022 0026-461X |
| DOI: | 10.1180/002646101550109 |
| Popis: | Lattice defects in lawsonite have been studied by transmission electron microscopy. It is proposed that twinning and easy glide systems are 1/2[110] {110}; the easy glide planes are coincident with twin planes. This mineral displays high sensitivity to the electron beam, even at low temperatures. In situ precipitates appear as a consequence of beam irradiation. The precipitation takes places first on dislocations, then on twin boundaries and then in the matrix, causing ‘coffee-bean’ contrast features typical of precipitates. The studies were performed at low temperature (∼110 K) in order to investigate the low temperature displacive transitions from space group Cmcm to Pmcn and P21cn and elucidate their microscopic character. No characteristic microstructural texture, such as antiphase domains associated with the transition, were observed, however. This is probably due to the high mobility of protons under the electron beam. The development of regularly spaced dislocations along twin planes is hypothesized as the only evidence that a phase transition takes place at a nanoscale. |
| Databáze: | OpenAIRE |
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