• S R Sawant

      Articles written in Bulletin of Materials Science

    • Dispersion of dielectric constant and resistivity of Cux Zn1−x Fe2O4 samples

      S R Sawant R N Patil

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      Cux Zn1−x Fe2O4 samples exhibit dispersion of dielectric constant, tanδ and resistivity in the frequency range of 1 kHz to 50 MHz. The dispersion exhibited is in general accord with Koops’ model. However, the details of the conducting and non-conducting regions must be taken into account when composition tends to change interrelationship between the elementary capacitor resistor circuits.

      On quenching these samples from 800°C the dielectric constantε1 showed an increase for CuFe2O4 and Cu0·8Zn0·2Fe2O4 samples. The dielectric constant of the remaining samples showed no influence on quenching. The compositional variation showed that the dielectric constant has higher value for the ferrite Cu0·4Zn0·6Fe2O4

      The results are explained on the basis of cation transfer.

    • A low-temperature attachment for a four-circle neutron diffractometer

      A Sequeira Sandhya Bhakay-Tamhane S R Sawant

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      A single-stage closed-cycle helium gas cryogenerator, capable of cooling between 77 K and 300 K, has been installed on the 4-circle neutron diffractometer at CIRUS. The cryo-tip assembly has been incorporated directly on the ϕ-circle of the full-circle crystal orienter in place of the goniometer head used in room temperature experiments. The salient features of this low-temperature attachment and its performance are discussed.

    • On the variation of a.c. susceptibility with temperature for some Cu-Li ferrites

      A B Naik S R Sawant S A Patil J I Powar

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      The a.c. susceptibility vs. temperature of the system (Li0·5Fe0·5)1−xCuxFe2O4, for 0⩽x⩽1·0 has been studied. While pure CuFe2O4 (x=1) shows a dramatic peak in susceptibility just before its Curie temperature (Tc), the same is supressed with the addition of a small amount of Li to the system. The variation of lattice parameter with Li content has also been investigated. Samples up tox=0·4 show tetragonal structure while those withx>0·4 are cubic. This change of structure can be explained on the basis of reduction ofdsp2 bonding of Cu ions on B-sites of the spinel lattice.

    • Conduction mechanism in Sn4+ substituted copper ferrite

      B L Patil S R Sawant S S Suryavanshi S A Patil

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      Thermoelectric power (α) and electrical resistivity (ρ) are reported for the system Cu1+xSnxFe2−2xO4 (wherex=0·05, 0·1, 0·15, 0·2 and 0·3) from room temperature to 800 K. The compositions withx=0·05 and 0·2 exhibitn-type conduction while the compositions withx=0·1 and 0·15 showp- ton-type conduction change after 423 K. The conduction at low temperature (i.e. < 400 K) is due to impurities, while at higher temperature (i.e. > 400 K), it is due to polaron. Hopping conduction phenomenon for the present system has been explained on the basis of localized model of electrons. Additional localization may arise due to Sn4+ + Fe2+ stable pairs at B-site and Cu1+ + Fe3+ pair at A-site.

    • Microstructure studies on Ti4+- and Zr4+-substituted Li-Zn ferrites

      R S Patil S S Suryavanshi S V Kakatkar A M Sankpal U R Ghodake S A Patil S R Sawant

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      XRD and microstructure studies were carried out on Ti4+ and Zr4+-substituted Li-Zn ferrites prepared by standard ceramic technique. All the ferrite compositions exhibit single phase formation. The lattice parametera increases linearly with the content of Zn2+Zr4+ and Zn2+Ti4+, which is attributed to the ionic volumes of the cations involved. With substitution by Zr4+ the average size decreases, while with substitution by Ti4+ the grain size increases. In both the series grain size varies with the composition. Excess substitution of Zr4+ (x>0·4) leads to the formation of secondary images and discontinuous grain growth. Both Zr4+ and Ti4+ compositions obey Kurtz theory.

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      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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