• S K Date

      Articles written in Bulletin of Materials Science

    • Comparison of the irreversible thermomagnetic behaviour of some ferro- and ferrimagnetic systems

      P S Anil Kumar P A Joy S K Date

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      The magnetic behaviour of two ferromagnetic oxides and two ferrimagnetic oxides (ferrites) are compared to study the effect of magnetocrystalline anisotropy on thermal-history-dependence of magnetization of these ordered magnetic systems. All four compounds show thermomagnetic irreversibility (MFC >MZFC) below a certain temperature,Tirr. The highly anisotropic ferromagnetic oxide, SrRuO3 and the hard ferrite, SrFe12O19 show sharp peaks belowTc in theirMZFC(T) curves, whereas for the soft ferrite Ni0.8Zn0.2Fe2O4 and the low anisotropic ferromagnetic oxide La0.7Ca0.3MnO3 only a broad maximum is observed inMZFC, when measured in small magnetic fields. The shapes of theMZFC(T) curves are inversely-related to the magnitude of the coercivities (Hc) of the compounds in relation to the applied field, and the temperature dependence of Hc.MFC andMZFC are related through the coercivity for all four magnetic systems.

    • Non-linear 𝐼–𝑉 characteristics of doped Sn1–𝑥Ti𝑥O2 (0.0 < 𝑥 < 0.25) system

      V Ravi S K Date

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      The solid solutions of Sn1–𝑥Ti𝑥O2 (0.0 < 𝑥 < 0.25) were prepared by the usual high temperature ceramic processing techniques with small amounts of dopants such as Nb, Co, Al. The electrical measurements (log 𝐼–log 𝑉) on the ohmically metal electroded sintered pellets showed the non-linear behaviour. The nonlinear coefficient was found to decrease from 12 to 3 with increase in 𝑥. On the other hand, the breakdown voltage (𝐸b) showed the increase with the increase in 𝑥. This complex electrical behaviour is explained on the effects of the three dopants (as varistor former, performance enhancer and highlighter) on the microstructural features of the dense pellet.

    • A new combustion route to 𝛾-Fe2O3 synthesis

      A Venkataraman Vijay A Hiremath S K Date S D Kulkarni

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      A new combustion route for the synthesis of 𝛾-Fe2O3 is reported by employing purified 𝛼-Fe2O3 as aprecursor in the present investigation. This synthesis which is similar to a self propagation combustion reaction, involves fewer steps, a shorter overall processing time, is a low energy reaction without the need of any explosives, and also the reaction is completed in a single step yielding magnetic iron oxide i.e. 𝛾-Fe2O3. The as synthesized 𝛾-Fe2O3 is characterized employing thermal, XRD, SEM, magnetic hysteresis, and density measurements. The effect of ball-milling on magnetic properties is also presented.

    • Tailoring magnetic and dielectric properties of rubber ferrite composites containing mixed ferrites

      M R Anantharaman K A Malini S Sindhu E M Mohammed S K Date S D Kulkarni P A Joy Philip Kurian

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      Rubber ferrite composites containing various mixed ferrites were prepared for different compositions and various loadings. The magnetic and dielectric properties of the fillers as well as the ferrite filled matrixes were evaluated separately. The results are correlated. Simple equations are proposed to predetermine the magnetic and dielectric properties. The validity of these equations is verified and they are found to be in good agreement. These equations are useful in tailoring the magnetic and dielectric properties of these composites with predetermined properties.

    • Preparation of microwave dielectric, Sn0.2Zr0.8TiO4

      Sanjay R Dhage V Ravi S K Date

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      A simple coprecipitation technique is described for the preparation of tin substituted zirconium titanate ceramic powders.

    • Nonlinear 𝐼–𝑉 characteristics study of doped SnO2

      S R Dhage V Ravi S K Date

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      When tin oxide is doped with Sb2O3 and CoO, it shows highly nonlinear current (𝐼)–voltage (𝑉) characteristics. Addition of CoO leads to creation of oxygen vacancies and helps in sintering of SnO2. Antimony oxide acts as a donor and increases the conductivity. The results are nearly the same when antimony oxide is replaced by tantalum oxide. The observed nonlinear coefficient, 𝛼 = 30 and the breakdown voltage is 120 V/mm.

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