• D K Kulkarni

      Articles written in Bulletin of Materials Science

    • Structural and magnetic properties of CaMg2Fe16O27

      P S Sawadh D K Kulkarni

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      A new compound, CaMg2Fe16O27, is synthesized for the first time, in polycrystalline form, using stoichiometric mixture of oxides with standard ceramic technique and characterized by X-ray diffraction. It is found to have a hexagonal W-type structure with lattice parameters 𝑎 = 5.850 Å and 𝑐 = 33.156 Å. Electrical studies show that the compound is a semiconductor with energy of activation, 𝛥 𝐸 = 0.56 eV. Electrical conductivity results show a transition in the conductivity vs temperature plot near the Curie temperature. The activation energy value obtained for the paramagnetic phase is found to be higher than that of the ferrimagnetic phase. The molar magnetic susceptibility was measured in the temperature range 300–850 K and the results show that the compound is ferrimagnetic at room temperature. The compound also shows hysteresis at 300 K. Paramagnetic nature of the sample above Curie temperature is also studied. The Curie molar constant 𝐶𝑀 calculated from the plot of 1/𝜒𝑀 vs 𝑇(𝐾) is found to be nearly in agreement with the expected value.

    • Preparation and study of thickness dependent electrical characteristics of zinc sulfide thin films

      A U Ubale D K Kulkarni

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      Zinc sulfide thin films have been deposited onto glass substrates by chemical bath deposition. The various deposition parameters such as volume of sulfide ion source, pH of bath, deposition time, temperature etc are optimized. Thin films of ZnS with different thicknesses of 76–332 nm were prepared by changing the deposition time from 6–20 h at 30°C temperature. The effect of film thickness on structural and electrical properties was studied. The electrical resistivity was decreased from 1.83 × 105 𝛺-cm to 0.363 × 105 𝛺-cm as film thickness decreased from 332 nm to 76 nm. The structural and activation energy studies support this decrease in the resistivity due to improvement in crystallinity of the films which would increase the charge carrier mobility and decrease in defect levels with increase in the thickness.

    • Characterization of nanocrystalline cadmium telluride thin films grown by successive ionic layer adsorption and reaction (SILAR) method

      A U Ubale R J Dhokne P S Chikhlikar V S Sangawar D K Kulkarni

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      Structural, electrical and optical characteristics of CdTe thin films prepared by a chemical deposition method, successive ionic layer adsorption and reaction (SILAR), are described. For deposition of CdTe thin films, cadmium acetate was used as cationic and sodium tellurite as anionic precursor in aqueous medium. In this process hydrazine hydrate is used as reducing agent and NH4OH as the catalytic for the decomposition of hydrazine. By conducting several trials optimization of the adsorption, reaction and rinsing time duration for CdTe thin film deposition was done. In this paper the structural, optical and electrical properties of CdTe film are reported. The XRD pattern shows that films are nanocrystalline in nature. The resistivity is found to be of the order of 4.11 × 103 𝛺-cm at 523 K temperature with an activation energy of ∼ 0.2 eV. The optical absorption studies show that films have direct band gap (1.41 eV).

    • Size dependent optical characteristics of chemically deposited nanostructured ZnS thin films

      A U Ubale V S Sangawar D K Kulkarni

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      ZnS thin films of different thicknesses were prepared by chemical bath deposition using thiourea and zinc acetate as S2- and Zn2+ source. The effect of film thickness on the optical and structural properties was studied. The optical absorption studies in the wavelength range 250–750 nm show that band gap energy of ZnS increases from 3.68–4.10 eV as thickness varied from 332–76 nm. The structural estimation shows variation in grain size from 6.9–17.8 nm with thickness. The thermoemf measurement indicates that films prepared by this method are of 𝑛-type.

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