The electrical properties of ferroelectric $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_{3}$ (PZT) and ferromagnetic $\mathrm{Co}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ (CFO) thin film multilayers (MLs) fabricated by pulsed laser deposition technique has been studied by impedance and modulus spectroscopy. The effect of various PZT/CFO configurations having three, five, and nine layers has been systematically investigated. The transmission electron microscopy images revealed that the ML structures were at least partially diffused near the interface. Diffraction patterns indicate clear PZT and CFO crystal structures in the interior and at the interface of the ML structure. Room temperature micro-Raman spectra indicate separate PZT and CFO phases in ML structure without any impurity phase. We studied frequency and temperature dependencies of impedance, electric modulus, and ac conductivity of ML thin films in the ranges of $100\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}\char21{}1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$ and $200\char21{}650\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively. We observed two distinct electrical responses in all the investigated ML films at low temperature $(l400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ and at elevated temperature $(g400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. We attributed these contributions to the grain effects at low temperature and grain boundary effects at high temperature. We explained this electrical behavior by Maxwell-Wagner-type contributions arising from the interfacial charge at the interface of the ML structure. Master modulus spectra indicate that the magnitude of grain boundary compared to grain becomes more prominent with the increase in the number of layer. The frequency dependent conductivity results well fitted with the double power law, $\ensuremath{\sigma}(\ensuremath{\omega})=\ensuremath{\sigma}(0)+{A}_{1}{\ensuremath{\omega}}^{{n}_{1}}+{A}_{2}{\ensuremath{\omega}}^{{n}_{2}}$, and the results showed evidence of three types of conduction process at elevated temperature: (i) low frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{kHz})$ conductivity is due to long-range ordering (frequency independent), (ii) midfrequency conductivity $(l10\phantom{\rule{0.3em}{0ex}}\mathrm{kHz})$ may be due to the short-range hopping, and (iii) high frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz})$ conduction is due to the localized relaxation hopping mechanism.

Impedance spectroscopy of multiferroic Pb Zr x Ti 1 − x O 3 ∕ Co Fe 2 O 4 layered thin films

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Physica. B, Condensed matter

Impedance studies of Sr modified BaZr0.05Ti0.95O3 ceramics

Impedance and electric modulus analysis of Sm-modified Pb(Zr0.55Ti0.45)1−x/4O3 ceramics

In this paper, we report some physical properties of AgAlP2O7 compound obtained through the standard solid-state reaction technique. AgAlP2O7 has been studied by X-ray diffraction, Raman spectroscopy and impedance spectroscopy. The title compound crystallized at room temperature (T = 300 K) in the monoclinic system with P21/c space group. The electrical properties were studied over a wide range of temperature (440–640 K) in the frequency range of 40 Hz–10 MHz. Study of frequency dependence of AC conductivity suggests that the material obeys the Jonscher’s universal dynamic law. The conductivity is equal to 9.37 × 10−5 Ω cm−1 at 640 K, and it is thermally activated with activation energy of 0.76 eV. The variation of DC conductivity with temperature follows the Arrhenius behavior. The calculated values of s decreased with temperature. This behavior reveals that the conduction mechanism is correlated with barrier hopping. The binding energy W
 m and the hopping distance R
 ω were deduced.

Conductivity study and correlated barrier hopping (CBH) conduction mechanism in diphosphate compound

The electrical properties of polycrystalline Bi6Fe2Ti3O18 are investigated by impedance spectroscopy in the temperature range 30–550°C. The imaginary part of impedance as a function of frequency shows Debye like relaxation. Impedance data are presented in the Nyquist plot which is used to identify an equivalent circuit and the fundamental circuit parameters are determined at different temperatures. The grain and grain-boundary contributions are estimated. The results of bulk a.c. conductivity as a function of temperature and frequency are presented. The activation energies for the a.c. conductivity are calculated. The polaron hopping frequencies are estimated from the a.c. conductivity data.

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Impedance spectroscopy study of polycrystalline Bi6Fe2Ti3O18

The dielectric and piezoelectric properties of SrBi4−xHoxTi4O15 (x=0.00, 0.02, 0.04 and 0.06) ceramics were investigated. SrBi4−xHoxTi4O15 (x=0.00, 0.02, 0.04 and 0.06; SBHT-x) ceramics were synthesized by the conventional solid state reaction sintering method. An X-ray diffraction measurement indicated that a single phase layered perovskite was obtained for all compositions. Studies of dielectric properties with temperature at different frequencies and piezoelectric properties have been carried out.

Dielectric and piezoelectric properties of SrBi4−xHoxTi4O15 (x=0.00, 0.02, 0.04 and 0.06) ceramics

Polycrystalline SrBi4Ti4O15 (SBiT) ceramics have been synthesized by a sol–gel method These ceramics were structurally characterized by powder x-ay diffraction studies (XRD), Rietveld analyses and scanning electron microscopy (SEM) The XRD pattern of SBiT crystallized into an orthorhombic structure with A21 am as space group The lattice parameters were calculated by Rietveld refinement SEM images of SBiT show plate-like grains with random orientation of plate faces Dielectric properties as a function of temperature at different frequencies are reported for this ceramic Poling experiments were carried out to determine the piezoelectric coefficients The conductivity of sintered ceramic was studied using impedance spectroscopy Cole–Cole plots show the presence of two semicircular arcs, suggesting the existence of grain and grain boundary effects

Synthesis and electrical properties of SrBi4Ti4O15 piezoelectric ceramics

Dielectric and ferroelectric properties of chemically synthesized and sintered lead lanthanum zirconate titanate and lead zirconate titanate discs were studied. The as-burnt powders were directly sintered to 94% and 96% of the theoretical density at 1100 °C and 1200 °C, respectively for lead lanthanumm zirconate titanate (PLZT) and 96.7% at 1100 °C for lead zirconate titanate (PZT). The sintered PLZT samples showed improved dielectric properties whereas PZT showed improved ferroelectric properties compared with the data reported in the literature. Dielectric permittivity at room temperature of the 1100 °C sintered PLZT sample with grain sizes 0.4–1.2 µm was ~5000, at all measured frequencies. Evaporation of PbO from the sample generated micro inhomogeneity, which was detrimental for the dielectric property. A sintered PLZT sample underwent a completely diffused phase transition whereas a sintered PZT sample underwent a partially diffused phase transition. The measured values of remnant polarization of the 1100 °C sintered PZT and PLZT samples were 54.0 and 40.0 µC cm−2, respectively. The coercive fields observed for these samples were 13.3 and 7.7 kV cm−1, respectively.

Dielectric properties of chemically synthesized PLZT and PZT: diffused phase transition and effect of lead non-stoichiometry

Sr0.2Na0.4Nd0.4Bi4Ti4O15 is prepared by Sol-Gel route using the modified polymeric precursor method based on the Pechini process and its electrical properties are investigated by Complex Impedance Spectroscopy (CIS). Results are presented in two ways, complex plane plots (real versus imaginary) and spectroscopic plots (real and imaginary against frequency). CIS has provided convincing evidence for the existence of both grain (bulk) and grain-boundary effects that were separated in the frequency domain of the impedance spectrum. Experimental data are fitted to two parallel RC equivalent circuits in series. The values of resistance and capacitance of bulk and grain boundary contributions are also calculated. Relaxation times are calculated for both grains and grainboundaries. Conduction and charge carrier behaviors are studied from frequency and temperature dependence of ac conductivity. The ac conductivity follows a two-power law behavior at different temperatures with frequency exponents s1 and s2. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

P. Sarah

Papers

Impedance spectroscopy study of polycrystalline Bi6Fe2Ti3O18

Dielectric and piezoelectric properties of SrBi4−xHoxTi4O15 (x=0.00, 0.02, 0.04 and 0.06) ceramics

Synthesis and electrical properties of SrBi4Ti4O15 piezoelectric ceramics

Dielectric properties of chemically synthesized PLZT and PZT: diffused phase transition and effect of lead non-stoichiometry

Impedance spectroscopy of Na and Nd doped strontium bismuth titanate