Anomalous elastic behaviour of xSrO-10PbO-(90-x)B2O3 glass system

• Borate anomaly in doped borate glass was investigated by elastic characterization.
• BO4 formation strengthened the glass network at lower concentrations of SrO.
• Higher NBO formation at higher SrO concentration weaken the glass structure.
• Ring deformation decreased within borate anomaly region due BO4 formation.

Glass samples with composition xSrO-10PbO-(90-x)B2O3 (x = 20, 25, 30, 35, 40 and 45) were prepared by melt-quenching method to elucidate the elastic behaviour due to borate anomaly. Structural investigation of glass samples were carried out by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy while elastic properties were studied by measuring both longitudinal and shear velocities using pulse-echo method at 5 MHz frequency. FTIR analysis revealed the presence of BO4 and BO3 vibration groups. Addition of SrO has resulted in increased ultrasonic velocities, elastic moduli (CL, μ, K and Y), hardness (H), Debye temperature (θD) for SrO content up to 30% but decreased for higher SrO addition. The fraction of the four coordinated boron atoms (N4) values, calculated from FTIR spectra increased for x ≤ 30 mol% followed by decrease at x > 30 mol%. Quantitative analysis of ultrasonic data using the bulk compression and ring deformation models showed reduction in the ratio of calculated bulk modulus to the experimental bulk modulus, Kbc/Ke for x ≤ 30 mol% indicating decreased ring deformation in borate anomaly region.