Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO sub(3)

Monodomain and periodically poled LiNbO sub(3) crystals (congruent composition) show dielectric and piezoelectric resonances between 100K and 900K. Dielectric measurements show resonances in some samples between 10-100kHz. These resonances vanish under thermal anneal in monodomain crystals while the...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2016-01, Vol.28 (1)
Main Authors: Nataf, Guillaume F, Aktas, Oktay, Granzow, Torsten, Salje, Ekhard K H
Format: Article
Language:English
Subjects:
Annealing
Crystal defects
Crystals
Dielectrics
Domain walls
Hardening
Piezoelectricity
Walls
Online Access:Get full text
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Summary:Monodomain and periodically poled LiNbO sub(3) crystals (congruent composition) show dielectric and piezoelectric resonances between 100K and 900K. Dielectric measurements show resonances in some samples between 10-100kHz. These resonances vanish under thermal anneal in monodomain crystals while they remain stable in periodically poled samples with high domain wall densities. The low activation energy of 0.18eV suggests their electronic (bi-polaronic) origin. Resonant piezoelectric spectroscopy, RPS, shows two features in virgin samples: a relaxation peak at 420K and a rapid hardening when the sample was slowly heated to ~500K. The dynamic relaxation and the hardening are related to excitations and reorientations of Li defects. The relaxations and hardening are irreversibly suppressed by high temperature anneal. We do not observe domain wall related RPS resonances in annealed samples, which excludes the existence of highly charged walls. We suggest that domain walls stabilize polaronic states with (bi-)polarons located inside or near to the ferroelectric domain walls.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/28/1/015901