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161 results on '"Roucau, C."'

1. New Incommensurate Elongated-Triangle Phase in Quartz

Author

Saint-Gregoire, P., Luk'yanchuk, I., Snoeck, E., Roucau, C., and Janovec, V.

Subjects
Condensed Matter
Abstract

We present for the first time the evidence for a thermodynamically stable incommensurate elongated-triangle ($ELT$) phase in quartz observed by transmission electron microscopy at structural $\alpha -\beta $ transition. The phase sequence on cooling is: uniform $\beta $ phase - stripe incommensurate phase (ferroelastic) - incommensurate equilateral-triangle ($EQT$) phase (ferroelectric) - incommensurate $ELT$ (ferroelectric and ferroelastic) - uniform $\alpha $ phase. The $ELT$ blocks could be responsible for the large light scattering in the vicinity of $\alpha-\beta$ transition., Comment: 4 pages revtex file +3 uuencoded compressed postscript figures

Published
1995
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16. Electron-microscopy study of the triple-qto single-qphase transition in the incommensurate phase of quartz under stress

Author

Roucau C and Snoeck E

Subjects
Stress (mechanics), Phase transition, Materials science, Optics, Condensed matter physics, business.industry, law, Phase (matter), Intermediate state, Electron microscope, business, Quartz, law.invention
Abstract

The triple-q to single-q phase transition in quartz has been studied by electron microscopy using a heating straining device, stress being applied along the x axis. The interpretation of the experimental images obtained for small values of stress is in agreement with theoretical predictions. The presence of an intermediate state between the triple-q and single-q modulated phases has been observed for higher values of stress. It can be described as a double-q state where the two wave vectors are tilted from the y direction by an angle of +φ and-φ that decreases to 0 in the single-q stripe phase

Published
1992

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