Pyroelectric Properties of Real LiNbO₃ Single Crystals Grown
from a Congruent Melt

Yu. V. Shaldin^a, V. T. Gabriélyan^b†, and S. Matyjasik^c

^a Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninski pr. 59, Moscow, 119333 Russia

e-mail: yuri1999@rambler.ru

^b Research Institute of Laser Physics, St. Petersburg, 199034 Russia

^c International Laboratory of Strong Magnetic Fields and Low Temperatures, Wroclaw, Poland

Received June 20, 2007

Abstract—The temperature dependences of the pyroelectric coefficient of lithium niobate single crystals
grown from a congruent melt have been investigated in the range of 4.2–300 K. No anomalies were found at
low temperatures, and the experimental dependence is described well by the Debye–Einstein model, with T_D =
357 K and two pyroactive frequencies of 692 and 869 cm¹. Specific features of lithium niobate have been ana-
lyzed. Two sublattices, formed by two pairs of mesotetrahedra with (according to the symmetry conditions)
dipole and octupole moments, were selected in the structure. Their contributions to the total polarization differ
by an order of magnitude. Vacuum annealing of the samples leads to the occurrence of anomalies only at tem-
peratures over 280 K; these anomalities are interpreted as a manifestation of superionic conductivity.

PACS numbers: 77.70.+a, 77.84.-s

DOI: 10.1134/S1063774508050209

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