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Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO3.


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Authors

Nataf, Guillaume F 
Aktas, Oktay 
Granzow, Torsten 
Salje, Ekhard KH 

Abstract

Monodomain and periodically poled LiNbO3 crystals (congruent composition) show dielectric and piezoelectric resonances between 100 K and 900 K. Dielectric measurements show resonances in some samples between 10-100 kHz. 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 0.18 eV suggests their electronic (bi-polaronic) origin. Resonant piezoelectric spectroscopy, RPS, shows two features in virgin samples: a relaxation peak at 420 K and a rapid hardening when the sample was slowly heated to ~500 K. 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.

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Keywords

lithium niobate, domain wall, polarons

Journal Title

J Phys Condens Matter

Conference Name

Journal ISSN

0953-8984
1361-648X

Volume Title

28

Publisher

IOP Publishing
Sponsorship
Engineering and Physical Sciences Research Council (EP/K009702/1)
GFN and TG are grateful to National Research Fund (Luxembourg) for support (FNR/P12/4853155/Kreisel). EKHS is grateful to EPSRC for support (EP/K009702/1).