• Ch Durga Prasad

      Articles written in Bulletin of Materials Science

    • Electrical properties of the system lanthanum lead cobalt titanium oxide

      Devendra Kumar Ch Durga Prasad Om Parkash

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      Measurements of DC electrical resistivity and Seebeck coefficient on the perovskite system La1−xPbxδ Co1−xTixO3−δ for 0·2≤x≤0·9 have been made in the temperature range 300–800 K. AC conductivity,σa.c, of all the samples were measured as a function of temperature (300–573 K) and frequency (1 kHz-1 MHz). DC resistivity behaviour of all the samples is similar. However, the resistivity value, which varies over 5–6 orders of magnitude, depends on both the compositionx and the structure of the samples. All the samples exhibitp-type electronic conduction. The value of Seebeck coefficient,α, for samples withx≤0·5 initially increases with temperature up to a particular temperature. Above this temperature, the behaviour ofα for samples withx≤0·5 and for samples withx>0·5 over the entire temperature range is similar to that of La CoO3. All the samples exhibit frequency-dependent a.c. conductivity at low temperatures.

    • Dielectric behaviour of glasses and glass ceramics in the system BaO-PbO-TiO2-B2O3-SiO2

      R K Mandal Ch Durga Prasad O M Parkash Devendra Kumar

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      Glasses with varying molar ratios of PbO/BaO in the system BaO-PbO-TiO2-B2O3-SiO2 were prepared keeping (BaO + PbO)/TiO2 ratio equal to one. The glasses were ceramized by two-stage heat treatment. X-ray diffraction indicates that PbTiO3 crystallizes in lead-rich glasses while BaTiO3 precipitates in barium-rich compositions. Solid solution (Ba, Pb)TiO3 does not seem to crystallize over the entire range of compositions. Simultaneous presence of PbO and BaO in the initial glass composition reduces the yield of ferroelectric phase. Dielectric properties have been interpreted in terms of microstructural features.

    • Preparation and characterization of Ca1 −xLaxTi1 −xCoxO3 (0·00<x⩽0·50) system

      O M Parkash Ch Durga Prasad Devendra Kumar

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      The possibility of the formation of solid solution in the system Ca1 −xLaxTi1 −x CoxO3 forx⩽0·5 has been investigated. X-ray diffraction studies show that compositions withx=0·05, 0·1, 0·2, 0·3 and 0·5 prepared by the ceramic method are single-phase materials. All the compositions have a structure similar to CaTiO3 with a pseudo-cubic unit cell. Preliminary studies show that interfacial polarization contributes significantly to their dielectric constant.

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