• K D Mandal

      Articles written in Bulletin of Materials Science

    • Electrical behaviour of lanthanum- and cobalt-doped strontium stannate

      O M Parkash K D Mandal C C Christopher M S Sastry Devendra Kumar

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      Electrical properties of lanthanum- and cobalt-doped strontium stannate, SrSnO3, have been studied as a function of temperature. All the compositions investigated have cubic structure. Measurement of Seebeck coefficient in one of the cobalt-doped SrSnO3 sample shows that it exhibitsp-type conductivity. Results of AC conductivity measurements show that conduction occurs by hopping of charge carriers in lanthanum-doped samples and forx=0·01 in cobalt-doped sample. Inx=0·05 sample in cobalt-doped system, conduction seems to occur in extended states.

    • Dielectric properties of CaCu2.9Co0.1Ti4O12 and CaCu3Ti3.9Co0.1O12 ceramics synthesized by semi-wet route

      K D Mandal Alok Kumar Rai Laxman Singh Om Parkash

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      The effect of Co+2 doping on Cu+2 and Ti+4 sites in calcium copper titanate, CaCu3Ti4O12, has been examined. The doped compositions, CaCu3−𝑥Co𝑥Ti4O12 and CaCu3Ti4−𝑥Co𝑥O12 (𝑥 = 0.10) ceramics, were prepared by novel semi-wet route. In this method, calcium, copper and cobalt salts were taken in solution form and TiO2 was used in solid form. XRD analysis confirmed the formation of single-phase materials. Structure of CaCu3Ti4O12 does not change on doping with cobalt either on Cu-site or Ti-site and it remains cubic. Scanning electron micrographs (SEM) show average grain size of CaCu2.9Co0.1Ti4O12 to be larger than CaCu3Ti3.9Co0.1O12 ceramic. Energy dispersive X-ray spectroscopy (EDX) studies confined the purity of parent and Co-doped CaCu3Ti4O12 ceramics. Dielectric constant (𝜀r) and dielectric loss (tan 𝛿) of CaCu2.9Co0.1Ti4O12 is comparatively higher than that of CaCu3Ti3.9Co0.1O12 ceramic at all measured frequencies and temperatures.

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