• S A Patil

      Articles written in Bulletin of Materials Science

    • 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.

    • Conduction in Mn substituted Ni-Zn ferrites

      B V Bhise A K Ghatage B M Kulkarni S D Lotke S A Patil

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      The d.c. electrical resistivity ‘ρ’ and thermoelectric power ‘α’ are studied as a function of temperature for Mn substituted ferrites with general formula Zn0·3Ni0·7+xMnxFe2−2xO4. At lower Mn concentrations, the increase in d.c. resistivity is attributed to the hindering of Verwey mechanism Fe2+ ⇌ Fe3+ due to stable bonds of Mn3+ + Fe2+ pair. The decrease in resistivity at higher Mn concentrations (i.e. whenx > 0·15) is attributed to the formation of Mn3+ cluster and Ni2+ ⇌ Ni3+. The activation energy values show one to one correspondence with resistivity values. The compositional variation of thermoelectric power showsn-type behaviour for the samples withx < 0·2 whereasp-type behaviour for the samples withx ⩾ 0·2. Thepn transition is attributed to the formation of Ni3+, Fe2+ + vacancies which act asp-type carriers. The temperature dependences ofα, ρ, and mobility clearly confirm the conduction mechanism to be due to polaron hopping.

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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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