• S V Suryanarayana

      Articles written in Bulletin of Materials Science

    • Tetragonal to cubic phase transition in silver chlorate

      Vilas Deshpande S V Suryanarayana C Frantz

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      Silver chlorate crystallizes in the tetragonal system at room temperature. The crystal undergoes a reversible first order phase tronsition to a cubic phase at 139°C. The transition temperature along with the enthalpy change was determined by thedsc technique and the change of enthalpy was found to be 3·12 cal/g. The high temperature form as determined by x-ray powder diffractometric method was found to be primitive cubic with a lattice constant of 6·681 Å at 145°C.

    • X-ray line profile analysis of silver base Ag-Cd-In alloys

      S Venkat Reddy S V Suryanarayana

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      X-ray diffraction line profiles of five silver base ternary alloys in α-phase with varying atomic percentages of cadmium and indium were recorded in both cold-worked and annealed states of the samples. Detailed studies on the profiles involving peak shift, peak asymmetry and Fourier analysis of line shapes have been carried out to evaluate microstructural parameters such as deformation fault probabilities,rms strains and dislocation densities. It was found that the addition of indium has a marked effect in producing deformation fault probabilities in comparison to that of adding cadmium in ternary silver base alloys. Compound fault probability was found to be maximum for the alloy Ag-10Cd-15In.

    • Superconductivity in Na-doped Bi2Sr2CaCu2Oy system

      S V Suryanarayana B Gopala Krishna Ravichandra Gundakaram S Venkat Reddy

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      Samples with the nominal composition Bi2Sr2Ca1−xNaxCu2Oy (x=0, 0·1, 0·2 and 0·3) were prepared by solid-state reaction of the individual compounds. X-ray diffraction patterns indicate that the samples have a majority 2212 phase with 2223 also being present. From the DC four-probe resistance data, we have observed that the furnace-cooled samples show metallic behaviour while the quenched samples show superconductivity up to 97 K.

    • Effect of annealing and quenching on superconductivity in Pb and Sb-doped Bi2Sr2Ca2Cu3Ox

      S V Suryanarayana Ravichandra Gundakaram B Gopala Krishna S Venkat Reddy

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      Samples of the series Bi1·9−xPbxSb0·1Sr2Ca2Cu3Oy withx=0, 0·1, 0·2, 0·3 and 0·4 were prepared by the solid-state route. The X-ray and d.c. electrical resistivity data on furnace-cooled and quenched samples are presented. Though the starting composition is 2223, the end products were multiphase with 4334 as the major phase. A superconducting transition withTc=100K was observed in the pure 2223 sample after quenching. The furnace-cooled samples were metallic, while samples withx=0·1, 0·2 and 0·3 were superconducting after quenching. The amount of the 4334 phase decreases with increasing Pb content. Quenching seems to be favourable for the formation of the 4334 phase.

    • Studies on electrical conduction in Bi4SrTi4O15

      A R James G S Kumar T Bhimasankaram S V Suryanarayana

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      The ferroelectric Bi4SrTi4O15 has been synthesized and a study of the electrical (AC) conductivity was made on both poled and unpoled samples in the frequency range from 100 Hz to 1 MHz and from room temperature to 550°C. In the case of unpoled samples the activation energy was found to be 0·54 eV and subsequent to poling it was lowered to 0·39 eV indicating an increased conductivity after poling. Further the conductivity increased with increasing frequency and temperature. DC conductivity measurements were also carried out. Dielectric measurements indicate a peak in the dielectric constant at 530°C.

    • Foreword

      P Rama Rao K J Rao S L N Acharyulu Y R Mahajan S V Suryanarayana S Ranganathan

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    • Magnetoelectric interaction phenomena in materials

      S V Suryanarayana

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      Following the phenomenological approach of Landau and Lifshitz the existence of linear magnetoelectric effect in antiferromagnetic Cr2O3 was predicted by Dzyaloshinskii which was later experimentally confirmed by Astrov and Folenet al. Magnetoelectric phenomenon has been observed in several single-phase materials in which simultaneous electric and magnetic ordering coexists and in two-phase composites in which the participating phases are the ferroelectric and magnetic. The author’s group has recently undertaken a systematic study of the preparation, characterization and detection of the (ME)H output in a few single-phase materials and two-phase composites. This article describes the magnetoelectric phenomenon in general and recent work carried out in the author’s group.

    • Dielectric measurements in vanadium doped barium titanate

      A Hanumaiah T Bhimasankaram S V Suryanarayana G S Kumar

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      Ceramic samples of Li0·1Ba0·95(VxTi1−x)O3, wherex=0 to 0·2 were prepared by solid state reaction method. The samples were characterized by XRD. The dielectric measurements have been carried out on the sintered disks as a function of the frequency (100 Hz-1 MHz) and temperature (300–420 K). The variation of dielectric constant with temperature indicates a diffuse phase transition in all the samples studied.

    • 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.

    • An experimental setup for dynamic measurement of magnetoelectric effect

      M Mahesh Kumar A Srinivas S V Suryanarayana G S Kumar T Bhimasankaram

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      An experimental setup is developed for the measurement of dynamic magnetoelectric effect (ME) in polycrystalline materials, using a time varying DC magnetic field on which an AC magnetic field is superimposed. The experimental data on ME on Bi5FeTi3O15 and a solid solution of (90%)BiFeO3-(10%)BaTiO3 are obtained using this setup. The linear and higher order ME coefficients can be evaluated from the output voltage. The temperature variation of ME data gives additional information corroborating with the data on magnetization.

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