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Ionic Displacements and Piezoelectric Constants of AgGaS2 from X-Ray Diffraction of a Crystal in an External Electric Field.

Published online by Cambridge University Press:  28 February 2011

Heinz Graafsma
Affiliation:
ChemistryDepartment, State University of New York at Buffalo, Buffalo, NY 14214
Jarek Majewski
Affiliation:
Weizmann Institute of Science, Rehovot, Israel
David Cahen
Affiliation:
Weizmann Institute of Science, Rehovot, Israel
Philip Coppens
Affiliation:
ChemistryDepartment, State University of New York at Buffalo, Buffalo, NY 14214
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Abstract

We have determined the displacements of the ions and the changes in cell parameters which occur on application of an electric field to a crystal of AgGaS2, using a three-step modulation method. The shifts in Bragg angle of 14 reflections, due to a fieldof 2.6 x 106 V/m applied nearly parallel to [221], were used to refine the change in cell parameters. The resulting piezo-electric coefficients are d14=d25 =8.8 (0.9) 10-12 C/N and d36=7.6 (1.8) 10-12 C/N. This leads to a value of 4.8 (0.5) pC/Nfor the piezoelectric constant in the [221] direction which compares well with a value of 5-6 10-12 C/N determined by other methods. The ionic displacements were studied on a second sample, with E=2.6x 106 V/m in adirection parallel to [110]. Very small, but significant a and b directiondisplacements were observed for all atoms, whereas the displacements in the c direction were negligible as expected. Relative to the sulfur framework, the Ga ion displacement is considerably larger than that of the Ag ions.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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