• R V Anavekar

      Articles written in Bulletin of Materials Science

    • Elastic properties and spectroscopic studies of Na2O–ZnO–B2O3 glass system

      V C Veeranna Gowda R V Anavekar

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      Elastic properties, 11B MAS–NMR and IR spectroscopic studies have been employed to study the structure of Na2O–ZnO–B2O3 glasses. Sound velocities and elastic moduli such as longitudinal, Young’s, bulk and shear modulus have been measured at a frequency of 10 MHz as a function of ZnO concentration. Both sound velocities and elastic moduli increase with increasing ZnO concentration. Poisson’s ratio and Debye temperature were also found to increase with ZnO concentration. 11B MAS–NMR and IR spectra show characteristic features of borate network and compositional dependence trends as a function of Na2O/ZnO concentration. The results are discussed in view of borate network and dual structural role of Zn2+ ion into the network. The results indicate that the Zn2+ ions are likely to occupy network forming positions in this glass system.

    • High field electrical behaviour in lithium–phospho–vanadate glass system

      C Narayana Reddy S Asokan R V Anavekar

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      The high field electrical switching behaviour of lithium–phospho–vanadate glasses has been studied by determining the current–voltage characteristics. The investigated glasses exhibit temperature, thickness and composition dependent trends. At low current, the 𝐼–𝑉 characteristics obey Ohm’s law followed by a negative resistance region where the bulk behaviour dominates and at higher values of current the sample goes to a low resistance state. The studied glasses exhibit memory type switching. It is suggested that electrical switching is due to the formation of conducting channels that are due to electronic origin while thermal effects dominate once the channels are formed resulting in crystallization.

    • Synthesis and structural studies of Na2O–ZnO–ZnF2–B2O3 oxyfluoride glasses

      Shantala D Patil V M Jali R V Anavekar

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      This paper describes the synthesis and spectroscopic studies of the glass system, 20Na2O–(20–𝑥) ZnO–𝑥ZnF2–60B2O3 (𝑥 = 0, 5, 10, 15, 20), prepared by melt quenching method. The analyses of DSC and XRD did not show the crystallinity of the glass sample. 11B MAS–NMR shows the presence of sharp peak around –14 ppm. From the IR studies, the broadening of the peak around 1200–1400 and 800–1100 cm-1 shows the presence of mixed linkages like B–O–B, B–O–Zn in the network.

    • Elastic properties of Na2O–ZnO–ZnF2–B2O3 oxyfluoride glasses

      Shantala D Patil V M Jali R V Anavekar

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      Elastic properties of Na2O–ZnO–ZnF2–B2O3 oxyfluoride glasses with different ZnF2 concentrations have been investigated using ultrasonic velocity measurements at room temperature, at a frequency of 10 MHz. Glasses prepared by melt quenching method were suitably polished for the ultrasonic velocity measurements using pulse-echo superposition method. Various elastic moduli have been calculated and their compositional dependence has been examined. The compositional dependence of elastic moduli with the concentration of ZnF2 shows decrease in the moduli initially, with further increase in ZnF2 the moduli sharply increases and then again tend to decrease when ZnF2 concentration is 20 mol%. The values of Poisson’s ratio lie in the range of 0.24–0.30, which is typical to covalent bonded network. The variation of 𝜃D with ZnF2 indicates complex behaviour of the glass network. The results have been analysed in view of the modified borate glass network. Addition of ZnF2 into the pure glass seems to influence the borate network by replacement of B–O–B linkages with B–O–Zn.

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