ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Electric fields with alternating square wave were applied to LiNbO3 and LiTaO3 single crystals in [001] directions, and extremely small ionic displacement was directly detected by the measurement of the diffracted intensities of X-rays synchronously with the applied fields. The displacement of Nb and Li ions relative to the oxygen framework were found to be 4.9 x 10-4 and 13 x 10-4 Å at E = 51.5 kV cm-1 for LiNbO3, and those of Ta and Li to be 6.8 x 10-4 and 15 x 10-4 Å at E = 50 kV cm-1 for LiTaO3. The temperature factor was observed to vary with the external field, which is attributed to the change in phonon frequency of the crystal lattice. It was found from the intensity variations in the lower-indexed reflections that the displacements of the bonding electrons of Nb-O and Ta--O bonds are much larger than those of the constituent ions, which may be the origin of the electrooptic effect. The capability of the modulation technique in the absolute structure determination of crystals is demonstrated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739482000710
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