H. S. Tewari

Study of the electrical conduction behaviour of the Ba1−xLaxTi1−xNixO3 (x ⩽ 0.10) system

Abstract The electrical conduction behaviour of the Ba 1− x La x Ti 1− x Ni x O 3 ( x ⩽ 0.10) system has been studied by complex plane impedance analysis and measurements of a.c. conductivity in the temperature range 400–575 K. The values of the bulk resistance for these samples are obtained from a circular arc passing through the origin in their impedance plots. A.c. conductivity obeys the relation σ a.c. αω 8 in the temperature range of measurements. These results indicate that conduction occurs in this system because of hopping of charge carriers between localized nickel sites.

Dielectric relaxator behaviour of Sr0.8La0.2Ti0.8Co0.2O3

Abstract Sr1−x La x Ti1−x Co x O3 for x ≤ 0.4 exhibits dielectric relaxator behaviour. The effect of firing temperature and different electroding on the dielectric properties of the sample Sr0.8La0.2Ti0.8Co0.2O3 has been investigated. Higher firing temperatures have no effect on the microstructure and on the resulting dielectric properties. On electroding with silver paint containing a low melting glass, CuO and Bi2O3 and heat-treating at 900 K for 15 minutes, the dielectric constant increased and the dielectric loss decreased. The dielectric characteristics have been analysed using complex plane impedance analysis.

Dielectric properties of the system Ca1−xYxTi1−xCoxO3(0.00 ⩽ x ⩽ 0.15)

The dielectric behaviour of the compositions withx⩽0.15 in the system Ca1−xYxTi1−xCoxO3 sintered and cooled in air has been studied. Space-charge polarization which arises due to the presence of chemical inhomogeneities at the micro-level contributes significantly to their dielectric constant. The composition with x=0.05 exhibits temperature and frequency-independent dielectric constant and very small dielectric loss.

Electrical conduction in calcium lanthanum titanium cobalt oxide, Ca1−xLaxTi1−xCoxO3 (x≤0.50)

The DC resistivity and the Seebeck coefficient have been measured as a function of temperature in the system Ca1-xLaxTi1-xCoxO3 for the samples with x<or=0.50 in the range 300-800 K. AC conductivity has been measured as a function of temperature and frequency for the samples with x<or=0.20 AC conductivity data indicate that conduction occurs due to hopping of charge carriers among localised sites giving rise to a Debye-type loss process at low temperatures. Results of AC resistivity combined with DC resistivity show that at high temperatures electrical transport occurs by excitation of charge carriers at the valance band edge and hopping at energies close to it.

Dielectric properties of the system Ca1 −x La x Ti1 −x Co x O3

Dielectric behaviour of samples of the system Ca1 −xLaxTi1 −xCoxO3 withx ⩽ 0·20 has been studied in the temperature range 300–525 K as a function of frequency. The strong dispersion ofɛ andD observed in these materials indicate the significant contribution of interfacial polarisation to the observed dielectric properties. The interfacial polarisation arises due to the presence of microscopic chemical heterogeneities arising out of the slow diffusion-controlled solid state sintering process used for their preparation.

Electrical conduction in calcium yttrium titanium cobalt oxide Ca1-xYxTi1-xCoxO3 (x<or=0.15)

The DC resistivity and Seebeck coefficient have been measured as a function of temperature in the system Ca1-xYxTi1-xCoxO3 for the samples with x<or=0.15 in the range 300-800 K. AC conductivity has been measured as a function of temperature and frequency. Results of these measurements show that electrical transport occurs mainly by a Debye-type loss process at temperatures less than 375 K and by excitation of charge carriers at localized states close to band edges and hopping among the localized sites.