Electrical behaviour of zirconium doped calcium copper titanium oxide

Abstract

In this investigation, the effect of Zr substitution at the Ti site of the CaCu3Ti4O12 on the electrical properties has been studied. Samples with composition x = 0.00, 0.10 and 0.30 have been synthesized by the solid state ceramic route in the system CaCu3Ti4−xZrxO12. Powder x-ray diffraction data showed the formation of a single phase solid solution. The structure remains cubic similar to an undoped sample. The Seebeck coefficient, α, is measured on a thick pellet in the temperature range 500–800 K and is found to be negative in this temperature range, indicating n-type conduction in the temperature range of measurement. Dc resistivity, ρdc, and ac conductivity, σac, were measured to understand the mechanism of conduction. Immittance analysis is used to separate the contributions of the grains and grain boundaries to the total observed resistance. From the temperature and frequency dependence of ac conductivity, it is concluded that at and around room temperature conduction occurs due to thermally activated rotation of dipoles while at high temperature it occurs due to excitation of charge carriers at the conduction band edge and hopping at energies close to it. From the immittance analysis it is observed that activation energies of conduction for grains and grain boundaries are almost equal indicating the same mechanism of conduction.

Composition‐Dependent Microstructures and Properties of La‐, Zn‐, and Cr‐Modified 0.675BiFeO3–0.325BaTiO3 Ceramics

“…Jumping of such oxygen vacancies around the oxygen octahedron will facilitate the reorientation of dipoles and contribute to dielectric constant . Different oxygen vacancy concentrations have different contribution to dielectric constant . Second, the embedded second phases form interfaces with BF–BT matrix, such interfaces may have low resistivity, indicated by the high dielectric loss in Fig.…”

Charge compensation, electrical and dielectric behavior of lanthanum doped CaCu3Ti4O12

“…With increase in temperature, these pairs of defects dissociate giving rise to free defect centres. Hopping of electrons among these defects, Cu + and Cu ++ will contribute to the long range migration of charge carriers i.e., excitation of charge carriers at conduction band edge and hoping at energies close to it, which leads to n-type conduction [19]. In this case, AC electrical conductivity is almost independent of frequency and exponentially dependent on temperature as expected [20].…”

“…At low temperature (near room temperature) due to Coulombic interaction, positively charged defects attract negativily charged defects. This leads the formation of associated defects pairs such as ( [19]. Hopping of electrons among copper ions of various valencies or of O 2− ions around Cu + /Cu ++ or Ti 4+ through vacant oxygen sites, V O •• will lead to the rotation of dipoles [19].…”

“…This leads the formation of associated defects pairs such as ( [19]. Hopping of electrons among copper ions of various valencies or of O 2− ions around Cu + /Cu ++ or Ti 4+ through vacant oxygen sites, V O •• will lead to the rotation of dipoles [19]. In the low temperature region, frequency dependent and temperature independent ac conductivity is observed because the hoping of charge carriers will lead to the rotation of dipoles [19,20].…”

“…Hopping of electrons among copper ions of various valencies or of O 2− ions around Cu + /Cu ++ or Ti 4+ through vacant oxygen sites, V O •• will lead to the rotation of dipoles [19]. In the low temperature region, frequency dependent and temperature independent ac conductivity is observed because the hoping of charge carriers will lead to the rotation of dipoles [19,20]. In other words, we can say that metal ion-oxygen vacancy complexes give rise to the defect states in the forbidden band gap.…”