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

Abstract

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.