Microwave synthesized zinc-boro-vanadate glasses: Structural elucidation by employing ultrasonic and MAS NMR studies
N. Sivasankarareddy, R. Viswanatha, B. Sujatha, C. Narayanaredd
Volume 2, Issue 4, Page 254-258, Year 2017 | DOI: 10.5185/amp.2017/410
Keywords: 11B MAS-NMR, borovanadate groups, ultrasound velocity, vickers hardness, elastic moduli.
Abstract: Correlation between mechanical properties and MAS NMR spectroscopic revelations have been carried out on the glass system, xZnO – 50 B2O3 – (50 – x) V2O5 where 15 ≤ x ≤ 40 is prepared by a novel microwave heating method. Elastic moduli were computed from ultrasound velocities measured by a pulse echo superposition method. Both ultrasound velocities and elastic properties increase monotonically as a function of ZnO content. The variations observed in the mechanical properties were explained in view of modifications occur in the network structure consisting of borovanadate units. The bulk and shear moduli increase due to the presence of four coordinated borons along with diborovanadate units, which increases the dimensionality and connectivity of the glass network. Surprisingly, the process of the reconversion of four coordinated borons into three coordinated borons beyond 33.3mol% of modifier concentration is not initiated in these glasses, which is essentially due to the formation of [B2V2O9]2- units similar to the [B4O7]2-units. This is well supported by the monotonic increase in N4 - values even above the 33.3 mol%of modifier content. Materials with enhanced elastic properties find application in cathode materials. Copyright © 2017 VBRI Press