• OM Prakash

      Articles written in Bulletin of Materials Science

    • Permeability spectrum of garnets

      Om Prakash R Aiyer C M Srivastava

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      A detailed study of permeability spectra of polycrystalline pure and Aland Gd-Substituted garnets has been carried out for different values of grain diameter and magnetisation. The spectra are of three types—resonance, relaxed and mixed. It has been shown that the resonance spectra occur when the closure demains are absent and the domain wall is anchored at the grain boundary. The relaxed spectrum is found for domains having closure flux while the mixed spectrum is an indication of simulataneous presence of grains with and without closure domains.

    • Wave-vector dependence of spin-wave line-width in yttrium iron garnets

      OM Prakash CM Srivastava

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      The wave-vector dependence of the spin-wave line-width in yttrium iron garnets has been studied for samples of grain diameter varying from 1·2µm to 12µm. An expression for the spin-wave line-width as a function of wave-vector and grain diameter has been obtained, which agrees satisfactorily with experiment.

    • Synthesis and microwave absorption studies of ferrite paint

      S M Abbas R P R C Aiyar OM Prakash

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      A new hexaferrite composition, BaCoxSix+yFe12−2x−yO19 (x=0·90;y=0·05), in fine (∼μ size) powder form, is prepared. Ferrite paint formulations are made by dispersing this powder in different weight proportions in an epoxy resin. X-band (8–12 GHz) microwave absorption behaviour of the paint coatings of different thicknesses is studied. Remarkably high value, ≥10 dB, of signal absorption at 9·5 GHz is observed for a coating thickness of 0·60 mm with a ferrite fill factor of 57 wt%.

    • Optical, mechanical and TEM assessment of titania-doped Bi2V1−𝑥Ti𝑥O$_{5.5−\delta}$ bismuth vanadate oxides

      Gurbinder Kaur Gary Pickrell Vishal Kumar Om Prakash Pandey Kulvir Singh Daniel Homa

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      Optical, mechanical and structural behaviors have been studied for titania-doped Bi2V1−𝑥Ti𝑥O$_{5.5−\delta}$ which are used as electrolytes for intermediate temperature fuel cells. Parameters like band gap ($E_{g}$), Urbach energy ($E_{u}$), refractive index, hardness (𝐻) and fracture strength (𝐾) have been calculated as a function of dopant concentration, i.e. 0.05 ≤ 𝑥 ≤ 0.2. Furthermore, analysis of transmission electron microscopy (TEM) images for all the oxides was conducted along with line spectra of planes. Results are discussed in light of correlation of these optical and mechanical parameters to their structural properties. Band gap has also been correlated to the conductivity of these oxides. Good correlation has been obtained between them.

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