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

Abstract

A series of BBCZr glass ceramics were synthesized by the usual melt-quenching technique and subsequent two-step heat treatment with the composition (in mol.%): 30Bi2O3-70B2O3 (pure sample) and (29-x)Bi2O3-70B2O3-1Cr2O3: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 (≈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 (≈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], BOB 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.