• Kamal Singh

      Articles written in Bulletin of Materials Science

    • A comparative study on the processing, dielectric and electrical properties of PMN based solid solutions

      Kamal Singh Sheela Band

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      Lead magnesium niobate (PMN) based binary with lead titanate (PT), lead iron niobate (PFN) and lead zinc niobate (PZN) and ternary with PZN-PT and PFN-PT solid solutions have been synthesized. In depth characterization using X-ray diffraction and SEM techniques have revealed the major perovskite phase formation. Amongst all the solid solutions, PMN-PZN-PT has given the highest values of permittivity as 19,740 and 23,700 withTc as 34°C when sintered at 1080°C and 1180°C respectively on the one hand and on the other, PFN containing solid solutions exhibited distinct deviation from the relaxor behaviour.

    • Effect of stoichiometry on the thermal expansion coefficients of lithium niobate single crystals

      Kamal Singh P V Saodekar S S Bhoga

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      The chemical analysis of LiNbO3 single crystals, with different melt compositions (Li/Nb)m=0·945, 1·0, 1·1 and 1·2, grown by slow cooling technique, reveals a remarkable difference in solid and melt compositions. The thermal expansion coefficients alonga andc axes, determined by using Newton’s ring experiment, are found to increase anisotropically with increase in (Li/Nb)m ratio. The variation in thermal expansion coefficient with increase in the (Li/Nb)m ratio is discussed in the light of defect chemistry i.e. the partial replacement of Li+ by excess Nb5+ creates additional cation vacancies to attain the electro-neutrality in the crystal.

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