Determination of the Distribution of the Relaxation Times from Dielectric Spectra

The dielectric susceptibility measurements are usually interpreted in terms of the relaxation times of various dynamical processes. Using the simple examples of the simulated spectra it is shown how the distribution of these relaxation times can be obtained by means of the integral equations solved with the Tikhonov regularization technique, and the criteria for the choice of the regularization parameter is discussed

Dielectric investigations of polycrystalline samarium bismuth ferrite ceramic

Results of broadband dielectric investigations of samarium doped bismuth ferrite ceramics are presented in wide temperature range (20–800 K). At temperatures higher than 400 K, the dielectric properties of samarium bismuth ferrite ceramics are governed by Maxwell-Wagner relaxation and electrical conductivity. The DC conductivity increases and activation energy decreases with samarium concentration. In samarium doped bismuth ferrite, the ferroelectric phase transition temperature decreases with samarium concentration and finally no ferroelectric order is observed at x = 0.2. At lower temperatures, the dielectric properties of ferroelectric samarium doped bismuth ferrite are governed by ferroelectric domains dynamics. Ceramics with x = 0.2 exhibit the relaxor-like behaviour

A study of random resistor-capacitor-diode networks to assess the electromagnetic properties of carbon nanotube filled polymers

We determined the frequency dependent effective permittivity of a large ternary network of randomly positioned resistors, capacitors, and diodes. A linear circuit analysis of such systems is shown to match the experimental dielectric response of single-walled carbon nanotube (SWCNT) filled polymers. This modeling method is able to reproduce the two most important features of SWCNT filled composites, i.e. the low frequency dispersion and dipolar relaxation. As a result of the modeling important physical conclusion proved by the experimental data was done: the low frequency behavior of SWCNT-filled polymer composites is mostly caused by the fraction of semiconducting SWCNTs

The polarizability model for ferroelectricity in perovskite oxides

This article reviews the polarizability model and its applications to ferroelectric perovskite oxides. The motivation for the introduction of the model is discussed and nonlinear oxygen ion polarizability effects and their lattice dynamical implementation outlined. While a large part of this work is dedicated to results obtained within the self-consistent-phonon approximation (SPA), also nonlinear solutions of the model are handled which are of interest to the physics of relaxor ferroelectrics, domain wall motions, incommensurate phase transitions. The main emphasis is to compare the results of the model with experimental data and to predict novel phenomena.Comment: 55 pages, 35 figure

ЭЛЕКТРОФИЗИЧЕСКИЕ И ДИЭЛЕКТРИЧЕСКИЕ СВОЙСТВА КОМПОЗИТОВ Pb0,85Zr0,53Ti0,47O3 - Sr2FeMoO6-δ

Ferromagnetic-ferroelectric composite materials on the base of Pb0.85Zr0.53Ti0.47O3-Sr2FeMoO6-δ (PZT-SFMO) compound have been prepared by a complex ceramic technology and the citrate-gel synthesis. It was determined that the dielectric permittivity of a sample with a content of PZT of 55 wt. % and SFMO of 45 wt. % increases with temperature due to the rise of electrical conductivity and an influence of the dielectric dispersion caused by the Maxwell-Wagner relaxation. The electrical conductivity of the sample with a content of PZT of 35 wt. % and a content of SFMO of 65 wt. % possesses a clearly expressed frequency dependence, at temperature lower than 600 K, whereas at higher temperatures the electrical conductivity almost does not depends on frequency in the range 20 Hz-1 MHz. This is concerned with a considerable decrease of critical frequency at higher temperatures. At frequencies higher than 100 kHz and temperature lower than 600 K, the electrical conductivity increases by a power law.C помощью комплексной керамической технологии и цитрат-гель синтеза изготовлены ферромагнитно-сегнетоэлектрические композиционные материалы на основе соединения Pb0,85Zr0,53Ti0,47O3-Sr2FeMoO6-δ (ЦТС-SFMO). Установлено, что диэлектрическая проницаемость образца с содержанием ЦТС - 55 вес. % и SFMO - 45 вес. % возрастает с температурой, вследствие роста электропроводности и влияния диэлектрической дисперсии, обусловленной релаксацией Максвелла - Вагнера. Электропроводность образца с содержанием ЦТС - 35 вес. % и SFMO - 65 вес. % имеет явно выраженную зависимость от частоты ниже температуры 600 K, в то время как при более высоких температурах электропроводность почти не зависит от частоты в диапазоне 20 Гц - 1 МГц. Это связано с существенным уменьшением критической частоты при более высоких температурах. При частотах выше 100 кГц и температуре ниже 600 K электропроводность возрастает по степенному закону

ОПТИМИЗАЦИЯ УСЛОВИЙ СИНТЕЗА КОМПОЗИТОВ ЦИРКОНАТА-ТИТАНАТА СВИНЦА БАРИЯ, СОДЕРЖАЩИХ АТОМЫ МЕТАЛЛОВ, И ИХ ДИЭЛЕКТРИЧЕСКИЕ СВОЙСТВА

Composition materials on the base of Pb0,75Ba0,15Zr0,53Ti0,47O3 (PBZT) with micro-inclusions of Cu and Ni are prepared by a complex ceramic technology. This technology includes metallization procedures by means of the chemical deposition method from standard solutions of nickel and copper. At determination of correlation of the structure of PBZT composites and their dielectric properties it was shown that dielectric losses increase with decreasing temperature. This is caused by the domination of the real part of the complex dielectric permittivity.C помощью комплексной керамической технологии, включающей процедуры металлизации методом химического осаждения из стандартных растворов никеля и меди, подготовлены композиционные материалы на основе соединения Pb0,75Ba0,15Zr0,53Ti0,47O3 (ЦТБС) с микро-включениями Cu и Ni. При установлении корреляций между структурой композитов ЦТБС и их диэлектрическими характеристиками показано, что при низких частотах диэлектрические потери возрастают с увеличением температуры, что обусловлено доминированием действительной части комплексной диэлектрической проницаемости