• Shashidhar Bale

      Articles written in Bulletin of Materials Science

    • Optical absorption and electron spin resonance studies of Cu2+ in Li2O–Na2O–B2O3–As2O3 glasses

      N Srinivasa Rao Shashidhar Bale M Purnima K Siva Kumar Syed Rahman

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      The local structure around Cu2+ ion has been examined by means of electron spin resonance and optical absorption measurements in 𝑥Li2O–(40 – 𝑥)Na2O–50B2O3–10As2O3 glasses. The site symmetry around Cu2+ ions is tetragonally distorted octahedral. The ground state of Cu2+ is $d_{x^2–y^2}$. The glass exhibited broad absorption band near infrared region and small absorption band around 548 nm, which was assigned to the ${}^{2}B_{1g} \rightarrow {}^{2}E_{g}$ transition.

    • Spectroscopic investigations of Cu2+ in Li2O–Na2O–B2O3–Bi2O3 glasses

      N Srinivasa Rao M Purnima Shashidhar Bale K Siva Kumar Syed Rahman

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      Pure and copper doped glasses with composition, 𝑥Li2O–(40–𝑥)Na2O–50B2O3–10Bi2O3, have been prepared over the range 0 < 𝑥 < 40. The electron paramagnetic resonance (EPR) spectra of Cu2+ ions of these glasses have been recorded in the X-band at room temperature. Spin Hamiltonian parameters have been calculated. The molecular bonding coefficients, 𝛼2 and 𝛽2, have been calculated by recording the optical absorption spectra in the wavelength range 200–1200 nm. It has been observed that the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The density and glass transition temperature variation with alkali content shows non-linear behaviour. The IR studies show that the glassy system contains BO3 and BO4 units in the disordered manner.

    • Mixed mobile ion effect on a.c. conductivity of boroarsenate glasses

      M Purnima Shashidhar Bale Ch Srinivasu M A Samee Syed Rahman

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      In this article we report the study of mixed mobile ion effect (MMIE) in boroarsenate glasses. DSC and a.c. electrical conductivity studies have been carried out for 𝑥MgO–(25−𝑥)Li2O–50B2O3–25As2O3 glasses. It is observed that strength of MMIE in a.c. conductivity is less pronounced with increase in temperature and frequency. The results were explained on the basis of structural model (SM) proposed by Swenson and his co-workers supporting molecular dynamic results.

    • Characterization and thermal expansion of Sr2Fe𝑥 Mo2−𝑥O6 double perovskites

      Y Markandeya Y Suresh Reddy Shashidhar Bale C Vishnuvardhan Reddy G Bhikshamaiah

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      Double perovskite oxides Sr2Fe𝑥Mo2−𝑥O6 (𝑥 = 0.8, 1.0, 1.2, 1.3 and 1.4) (SFMO) of different compositions were prepared by sol–gel growth followed by annealing under reducing atmosphere conditions of H2/Ar flow. X-ray powder diffraction studies revealed that the crystal structure of the samples changes from tetragonal to cubic at around 𝑥 = 1.2. Lattice parameters and unit cell volume of these samples found to decrease with the increase in Fe content. The characteristics absorption bands observed in the range 400–1000 cm−1 of Fourier transform infrared spectra indicate the presence of FeO6 and MoO6 octahedra and confirm the formation of double perovskite phase. The value of g ∼ 2.00 obtained from electron spin resonance studies indicates that Fe is in 3+ ionic state in the SFMO samples. Dilatometric studies of these samples reveal that the average value of coefficient of thermal expansion ($\overline{\alpha}$) increases with the increase in temperature or Fe content in SFMO samples. The low value of coefficient of thermal expansion 1.31 × 10−6°C−1 obtained for Sr2Fe0.8Mo1.2O6 in the present study in the temperature range of 40–100°C makes it useful as anode material in fuel cells. The coefficient of thermal expansion ($\overline{\alpha}$) and the unit cell volume (𝑉) of SFMO samples vary inversely with composition in agreement with Grüneisen relation.

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