Structural evolution of versatile Bi₂O₃-B₂O₃-Cr₂O3: ZrO₂ glass ceramics monitored by Raman and EPR spectroscopy

A series of BBCZr glass ceramics were synthesized by the usual melt-quenching technique and subsequent twostep heat treatment with the composition (in mol.%): 30Bi2O3-70B2O3 (pure sample) and (29-x)Bi2O3-70B2O31Cr2O3:xZrO2 (0 <= x <= 2). Morphological, physical, thermal, structural, and magnetic characteristics of BBCZr glass ceramics have been investigated with the various concentrations of zirconium oxide nanoparticles (approximate to 45 nm) in the composition. XRD and SEM studies have confirmed the existence of induced heterogeneous crystal phases in the glass ceramics. The Raman spectra have revealed the Boson peak at low frequencies (approximate to 62-72 cm 1), various functional groups of primary glass forming units like [BO4], [BiO3], [CrO4]2 and [ZrO4] units, and other glass modifying units/crystallite units viz., [BO3], [BiO6], [CrO6], B-O-B chains, etc. The Boson peak maximum has exhibited an anomalous dip at x = 1 mol.%, at which the glass ceramic sample exhibits more heterogeneous crystal phases. The paramagnetic isolated Cr3+ ions plus Cr3+-Cr3+ ion pairs were detected by EPR studies. The BBCZr glass ceramics may be useful for potential applications such as optical elements, paramagnetic sensing elements, etc.