• C R Gautam

      Articles written in Bulletin of Materials Science

    • IR study of Pb–Sr titanate borosilicate glasses

      C R Gautam Devendra Kumar Om Parkash

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      The infrared spectra (IR) of various glass compositions in the glass system, [(Pb𝑥Sr1–𝑥)O.TiO2]– [2SiO2.B2O3]–[BaO.K2O]–[La2O3], were recorded over a continuous spectral range (400–4000 cm-1) to study their structure systematically. IR spectrum of each glass composition shows a number of absorption bands. These bands are strongly influenced by the increasing substitution of SrO for PbO. Various bands shift with composition. Absorption peaks occur due to the vibrational mode of the borate network in these glasses. The vibrational modes of the borate network are seen to be mainly due to the asymmetric stretching relaxation of the B–O bond of trigonal BO3 units. More splitting is observed in strontium-rich composition.

    • Dielectric and impedance spectroscopic studies of (Sr1–𝑥Pb𝑥)TiO2 glass ceramics with addition of Nb2O5

      C R Gautam Devendra Kumar Om Parkash

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      Glasses were made by melt-quench method in the system [(Sr1–𝑥Pb𝑥)O.TiO2]–[2SiO2.B2O3]–5[K2O–BaO] (0.0 ≤ 𝑥 ≤ 0.4) with addition of 1 mol% Nb2O5. Perovskite strontium lead titanate in solid solution phase has been crystallized in borosilicate glassy matrix with suitable choice of composition and heat treatment schedule. Addition of 1 mol% of Nb2O5 enhances the crystallization of lead strontium titanate phase in the glassy matrix. Scanning electron microscopy (SEM) is performed to study the surface morphology of the crystallites and crystalline interface to the glass. Dielectric properties of these glass ceramics were studied by measuring capacitance and dissipation factor as a function of temperature at a few selected frequencies. Nb2O5 doped strontium lead titanate glass ceramic shows a high value of dielectric constant. It is of the order of 10,000 while the dielectric constant of undoped glass ceramic sample is of the order of 500. Complex impedance and modulus spectroscopic techniques were used to find out the contributions of polarization of crystallites and glass crystal interfaces to the resulting dielectric behaviour.

    • Synthesis, IR, crystallization and dielectric study of (Pb, Sr)TiO3 borosilicate glass–ceramics

      C R Gautam D Kumar O Parkash Prabhakar Singh

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      Eleven glass compositions were prepared by melt and quench method with progressive substitution of SrO for PbO (0 ≤ 𝑥 ≤ 1.0) with a step-wise increment of 0.10 in the glass [(Pb𝑥Sr1−𝑥)OTiO2]–[(2SiO2B2O3)]–[BaO.K2O].Nb2O5 (mol percentage) system. The infrared spectra (IR) of various glass compositions in the above mentioned glass system was recorded over a continuous spectral range 400–4000 cm-1 to study their different oxides structure systematically. Differential thermal analysis (DTA) was recorded from room temperature (∼27 °C) to 1400 °C employing a heating rate of 10 °C/min to determine glass transition temperature, 𝑇g and crystallization temperature, 𝑇c. The melting temperature, 𝑇m, of these glass compositions was found to be in the range 597–1060 °C depending on the composition under normal atmospheric conditions. 𝑇g and 𝑇m of glasses were found to increase with increasing SrO content. X-ray diffraction analysis of these glass–ceramic samples shows that major crystalline phase of the glass–ceramic sample with 𝑥 ≤ 0.5 was found to have cubic structure similar to SrTiO3 ceramic. Scanning electron microscopy has been carried out to see the surface morphology of the crystallites dispersed in the glassy matrix.

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      Posted on October 12, 2020

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      Chemical Sciences 2020

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