• N V Prasad

      Articles written in Bulletin of Materials Science

    • Dielectric properties of cobalt doped cadmium oxalate crystals

      N V Prasad G Prasad T Bhimasankaram S V Suryanarayana G S Kumar

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      CoxCd1−xC2O44H2O crystals grown by gel technique are characterized for dielectric properties by optical absorption measurements. Loss curve shows a relaxation peak at 500 KHz corresponding to a relaxation time of 0·3 µs. Cole-Cole diagrams give exponent of universal power law to be equal to 0·22. Optical absorption shows peaks due to Co+2 ion and water of hydration. An attempt is made to understand the results.

    • Dielectric studies on Sm-modified two-layered BLSF ceramics

      MD ABDUL BASHEER G PRASAD G S KUMAR N V PRASAD

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      Sm$_x$Bi$_{3−x}$TiNbO$_9$ (SBTN) with $x = 0$, 0.2, 0.4, 0.6, 0.8 and 1.0, a novel type of ceramic was prepared by a conventional solid-state reaction method. X-ray diffraction patterns confirm the formation of a single-phase, and lattice parameters were calculated based on the parent compound Bi$_3$TiNbO$_9$ (BTN). Well-defined grains were seen in the scanningelectron microscopy pictures. A kink observed near 400$^{\circ}$C for all the samples in the dielectric plot as well as in the stretched exponential parameter ($\beta$) vs. temperature plot reveals the dielectric relaxation of the samples. The tolerance factor ($t$) was found to increase with increase in the size of the A-site (Bi-site) modified ion (Sm). Impedance and modulus spectroscopicstudies were conducted to understand the plausible reason for the dielectric relaxation. The relaxation was found to be well-fit with Arrhenius equation. SBTN samples showed lower dielectric loss compared to BTN. The remnant polarization, obtained from experimental, was found to be less than that of theoretically calculated polarization, using Shimakawa’s formula. The proposed defect mechanism was interpreted using FTIR and Raman spectroscopic studies.

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