Dielectric Impedance Properties Research Articles

Electrical conductivity and impedance spectroscopy studies of ceramic (Ba0.8Sr0.2)Ti0.95(Zn1/3Nb2/3)0.05O3 doped with Bi2O3

Polycrystalline samples of (Ba0·8Sr0.2)1–3x/2BixTi0.95(Zn1/3Nb2/3)0.05O3 (BixBSTBZN) (x = 0.00, 0.10), were prepared by the solid state reaction method. The dielectric impedance properties were studied over the range of frequency between 100 Hz and 1 MHz and in the temperature range of 420 °C–480 °C, using the modulus formalism. The impedance plot showed a first semicircle at high frequency which was assigned to the grain intrinsic effect and a second semicircle, at lower frequencies, which corresponds to grain boundary polarization (conduction phenomenon). A complex modulus spectrum was used to understand the mechanism of the electrical transport process, which indicates that a non-Debye type of multiple relaxations in the material. The values of the activation energy of the compound (calculated both from dc conductivity and the modulus spectrum) are very similar, suggesting that the relaxation process may be attributed to the same type of charge carriers. The frequency dependent conductivity plots exhibit double power law dependence suggesting three types of conduction mechanisms: low frequency conductivity owing to long range translational motion of electrons, mid-frequency conductivity due to short-range hopping, and high frequency conduction due to localized orientation hopping mechanism. Variation of ac conductivity as a function of frequency shows that the compound exhibits Arrhenius-type of electrical conductivity.

Electrical conductivity and dielectric analysis of NaH2PO4 compound

The sodium dihydrogen phosphate NaH2PO4 can be obtained by slow evaporation at room temperature and characterized by X-ray powder diffraction, scanning electron microscopy (SEM), and electrical impedance spectroscopy. The X-ray diffraction pattern revealed that the sample presents a single phase that crystallizes in the monoclinic structure with a P21/c space group, and the unit cell parameters are a = 6.8034 A, b = 13.4014 A, c = 7.2986 A, and β = 92.827°. The dielectric impedance properties were studied over the range of frequency between 103 Hz and 1 MHz and in the temperature range of 300–440 K. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination of resistance (R), fractal capacitance (CPE), and capacitance (C). Furthermore, the frequency-dependent AC conductivity obeys Jonscher’s universal power law. In fact, the near values of activation energy obtained from the modulus spectra and conductivity confirm that the transport happens through a proton-hopping mechanism, dominated by the motion of the proton H+ in the structure of the investigated materials.

Impedance and modulus studies of magnetic ceramic oxide Ba2Co2Fe12O22 (Co2Y) doped with Bi2O3

Polycrystalline samples of a layered magnetic ceramic oxide, Ba2Co2Fe12O22 (Co2Y), doped with Bi2O3 were prepared by the solid state reaction method. The dielectric impedance properties were studied over the range of frequency between 1 Hz–1MHz and in the temperature range of 313–493 K, using the modulus formalism. The impedance plot showed a first semicircle at high frequency which was assigned to the grain intrinsic effect and a second semicircle, at lower frequencies, which corresponds to grain boundary polarization (conduction phenomenon). A complex modulus spectrum was used to understand the mechanism of the electrical transport process, which indicates that a non-exponential type of conductivity relaxation characterizes this material. The values of the activation energy of the compound (calculated both from dc conductivity and the modulus spectrum) are very similar, suggesting that the relaxation process may be attributed to the same type of charge carriers. The dielectric measurements were studied by fitting the electrical modulus with the Havriliak–Negami function, including the conductivity parameters. The study demonstrates that the investigation of dielectric relaxation, conductivity, and loss of the ferrite materials, as a function of temperature, are essential for future microwave absorption applications of this material.