• Aman

      Articles written in Bulletin of Materials Science

    • Optical absorption and fluorescent behaviour of titanium ions in silicate glasses

      Manoj Kumar Aman Uniyal A P S Chauhan S P Singh

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      Titanium in normal melting conditions in air atmosphere present as Ti4+ ion in basic silicate glasses exhibited an ultra-violet cut-off in silicate glasses, viz. soda–magnesia–silica, soda–magnesia–lime–silica and soda–lime–silica glasses. This indicates that Ti4+ ion can be a good replacement for Ce4+ ion in producing UV-absorbing silicate glasses for commercial applications. The wavelength maxima at which the infinite absorption takes place in glasses was found to be around 310 nm against Ti-free blank glass in UV-region. The mechanism of electronic transition from O2- ligands to Ti4+ ion was suggested as L $\rightarrow$ M charge transfer. The low energy tails of the ultra-violet cut-off were found to obey Urbach’s rule in the optical range 360–500 nm. The fluorescence spectra of these glasses were also studied and based on the radiative fluorescent properties it was suggested that the soda–lime–silica glass containing Ti4+ ion with greater emission crosssection would emit a better fluorescence than the corresponding soda–magnesia–lime–silica and soda–magnesia–silica glasses. The shift of emission wavelengths maxima towards longer wavelength in titania introduced silicate glasses was observed on replacement of MgO by CaO which may be attributed due to an increase in basicity of the glass system.

    • Comparative investigation on the effect of alkaline earth oxides on the intensity of absorption bands due to Cu2+, Mn3+ and Cr3+ ions in ternary silicate glasses

      S P Singh Aman Anal Tarafder

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      Absorption characteristics of Cu2+, Mn3+ and Cr3+ ions in ternary silicate (20Na2O.10RO.70SiO2, where R=Ca, Sr, Ba) glasses were investigated. The intensities of absorption bands due to Cu2+ ion was found to increase with increasing ionic radii of the alkaline earth ions whereas it was found to decrease in case of Mn3+ and Cr3+ ions with increasing ionic radii of the alkaline earth ions. The results were discussed in the light of relation between linear extinction coefficients of these ions and coulombic force of alkaline earth ions. The change in intensities of Cu2+, Mn3+ and Cr3+ ion is attributed due to change in silicate glass compositions.

    • Role of tin as a reducing agent in iron containing heat absorbing soda–magnesia–lime–silica glass

      Aman S P Singh

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      The role of tin as a reducing agent in a 18Na2O.2MgO.8CaO.72SiO2 glass containing a definite amount of total, 𝛴 Fe = [Fe2+] + [Fe3+], was investigated with different concentrations of total tin, 𝛴 Sn = [Sn2+] + [Sn4+], by absorption spectra of iron ions in the optical range 300–1200 nm recorded on a JASCO-7800 spectrophotometer. The single broad absorption band for Fe2+ ion was marked at 1055 nm in the near infrared region and a narrow weak band for Fe3+ ion at its 𝜆max at around 380 nm was observed in the silicate glass. The proportion of ferrous iron was found to increase in the glass in the beginning with the addition of tin up to 0.788% 𝛴 Sn and then it approached a maxima with 1.182% 𝛴 Sn. Further addition of tin was found to be futile for the constant iron concentration of 0.875% for achieving higher [Fe2+]/[Fe3+] ratio for maximum heat absorption due to Fe2+ ion in the glass. The mechanism of the process was discussed on the basis of Sn2+/Sn4+ and Fe2+/Fe3+ mutual redox interaction in the molten glass at 1400°C. The suitable limit of tin was suggested to be 0.788 ≤ 𝑥 ≤ 1.182% by wt for 0.875% of total iron for getting maximum ferrous ion in the glass.

    • Tuning of structural, morphological, optical and electrical properties of SnO$_2$ by indium inclusion


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      A complete range of indium-doped (In:SnO$_2$) thin films prepared by spray-pyrolysis technique have been studied and characterized by different techniques to get information about structure, surface and electrical properties. The influence of indium filler concentration (i.e., 0–15 wt%) on the properties of SnO$_2$ has been explored. Structural study reveals that the inclusion of indium after a certain optimum value leads structural distortion which causes the films’ expansion along c-axis direction. The extract of electrical study helps to understand that what should be the optimum value to switch from n- to p-type, which is further confirmed by Hall measurement. A deep analysis of electrical data confirms that the solid solution of indium into SnO$_2$ should not be completely excluded and its range should not be >12 wt% as we got saturation in the electrical behaviour after it. Variable range hopping mechanism has been found to be best fitted for low temperature range and comes out with valuable information that increase in density of states near Fermi level are responsible for decrease in resistivity in case of higher doping and also confirms that 6 wt% is the optimum value to switch from n- to p-type conductivity.

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    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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