Low Temperature Physics: 42, 805 (2016); https://doi.org/10.1063/1.4963387
Fizika Nizkikh Temperatur: Volume 42, Number 9 (September 2016), p. 1027-1034 ( to contents , go back )
Spontaneous polarization of nonstoichiometric LiIO3 crystals in the low-temperature region
International Laboratory of Magnetics Fields and Low Temperatures 95 Gajowicka Str., 53-421 Wroclaw, Poland
Институт кристаллографии РАН, Ленинский пр., 59, г. Москва, 119333, Россия
Received December 3, 2015, revised March 16, 2016
Results of measurements of a total charge of Q(T) = SΔPs(Т) in nonstoichiometric LiIO3 z-cut samples in the range of 4.2–300 K are given. The provided information has been supplemented with data due to the thermostimulated depolarization induced by external electric field of different value and polarity. At T over 130 K there are found anomalies of dependence of ΔPs (Т,U), caused, as a rule, by a deviation of structure of a crystal from a stoichiometry. The possible nature of a the nonstoichiometry has been specified according to the magnetic measurements which have allowed to detect interstitial Li below 100 K and also two paramagnetic associates at 25 K and 50 K of unknown nature. Temperature in-crease leads to ionization of lithium with formation of Li+ ions and associates (VO+2e)-, (VO++VLi-)+ responsible for the ionic conductivity. In the condition of charge measurement at T > 140 K the possibility of formation of the associates of other type (VLi-, Li+) having the dipolar moment directed opposite to ΔPs, isn't excluded. It is shown that in a limited interval of temperatures from 18 K to 35 K dependence of ΔPs on temperature ~ T4 corresponds to M. Born’s theory. The considerable fluctuations of a pуrocoefficient connected, at first glance, with a disorder of the crystal structure of nonstoichiometry sample leading to distribution of relaxation times of a defective subsystem elements are found.
PACS: 77.70.+а Pyroelectric and electrocaloric effects;
Key words: pyroelectric, nonstoichiometry, crystal model, spontaneous polarization.
Published online: July 25, 2016