Phase Transitions and Low-Frequency Dielectric Dispersion
in Ferroelectric LangmuirBlodgett Films
of the Copolymer Vinylidene Fluoride with Trifluoroethylene

S. P. Palto^1, *, A. M. Lotonov², K. A. Verkhovskaya¹, G. N. Andreev¹, and N. D. Gavrilova²

¹Institute of Crystallography, Russian Academy of Sciences, Moscow, 117333 Russia

²Moscow State University, Moscow, 119899 Russia

*e-mail: lev@glasnet.r

Received June 9, 1999

Abstract—The dielectric properties of multilayer ferroelectric Langmuir–Blodgett films based on the copoly-
mer vinylidene fluoride with trifluoroethylene with 70/30 composition are investigated. Good agreement with
theoretical models on the basis of the phenomenological Landau–Ginzburg approach is demonstrated for the
first time for ultrathin films. Expressions describing the temperature variation of the permittivity in the temper-
ature range of hysteresis and giving quantitative agreement with experimental data are obtained. It is shown that
the Langmuir–Blodgett films are conducting. This conductivity does not depend on the frequency of the field.
The results are explained by the fact that the motion of charge in the films is not bounded by domain walls. The
jumps observed in the frequency dispersion at volume and low-temperature (surface) phase transitions are
explained by a sharp increase in the relaxation times at the transition into the ferroelectric state. © 2000 MAIK
“Nauka/Interperiodica”.

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