• S K Deshpande

      Articles written in Bulletin of Materials Science

    • Conductivity studies of lithium zinc silicate glasses with varying lithium contents

      S K Deshpande V K Shrikhande M S Jogad P S Goyal G P Kothiyal

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      The electrical conductivity of lithium zinc silicate (LZS) glasses with composition, (SiO2)0.527 (Na2O)0.054(B2O3)0.05(P2O5)0.029(ZnO)0.34–𝑥(Li2O)𝑥 (𝑥 = 0.05, 0.08, 0.11, 0.18, 0.21, 0.24 and 0.27), was studied as a function of frequency in the range 100 Hz–15 MHz, over a temperature range from 546–637 K. The a.c. conductivity is found to obey Jonscher’s relation. The d.c. conductivity ($\sigma_{d.c.}$) and the hopping frequency($\omega_{h}$), inferred from the a.c. conductivity data, exhibit Arrhenius-type behaviour with temperature. The electrical modulus spectra show a single peak, indicating a single electrical relaxation time, 𝜏, which also exhibits Arrhenius-type behaviour. Values of activation energy derived from $\sigma_{d.c.}, \omega_{h}$ and 𝜏 are almost equal within the experimental error. It is seen that $\sigma_{d.c.}$ and $\omega_{h}$ increase systematically with Li2O content up to 21 mol% and then decrease for higher Li2O content, indicating a mixed alkali effect caused by mobile Li+ and Na+ ions. The scaling behaviour of the modulus suggests that the relaxation process is independent of temperature but depends upon Li+ concentration.

    • X-ray reflectivity study of bias graded diamond like carbon film synthesized by ECR plasma

      R M Dey S K Deshpande S B Singh N Chand D S Patil S K Kulkarni

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      Diamond like carbon (DLC) coatings were deposited on silicon substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using plasma of Ar and CH4 gases under the influence of negative d.c. self bias generated on the substrates by application of RF (13.56 MHz) power. The negative bias voltage was varied from −60 V to −150 V during deposition of DLC films on Si substrate. Detailed X-ray reflectivity (XRR) study was carried out to find out film properties like surface roughness, thickness and density of the films as a function of variation of negative bias voltage. The study shows that the DLC films constituted of composite layer i.e. the upper sub surface layer followed by denser bottom layer representing the bulk of the film. The upper layer is relatively thinner as compared to the bottom layer. The XRR study was an attempt to substantiate the sub-plantation model for DLC film growth.

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