Structure and crystallization kinetics of Bi2O3–B2O3 glasses

Abstract

The experimental IR (infrared spectra) and differential scanning calorimetry (DSC) curves of Bi2O3–B2O3 glasses, containing 30–60mol% Bi2O3, have been investigated in the article. The composition dependence of IR absorption suggests that addition of Bi2O3 results in a change in the short-range order structure of the borate matrix. The increase of Bi2O3 content causes a progressive conversion of [BO3] to [BO4] units. Bi2O3, in the form of [BiO6] octahedral units, plays the role of glass former. The crystallization kinetics of Bi2O3–B2O3 glasses were described by thermal stability indexes (kgl, ΔT), activation energy (E) for crystallization and numerical factors(n, m) depending on the nucleation process and growth morphology, which were calculated by Šatava method and the modified Ozawa–Chen method. When Bi2O3≤45mol%, the increase of Bi2O3 tends to improve the thermal stabilities of the glasses. In this case, kgl may be more suitable for estimating the glass thermal stability in above composition range than ΔT. A further increase of Bi2O3 content will increase the crystallization trends of investigated glasses. Two possible kinds of growth mechanisms were involved in Bi2O3–B2O3 glasses: one-dimensional growth and two-dimensional growth. Moreover, structures of crystallized glasses were observed by X-ray diffraction (XRD). BiBO3 crystal with special non-linear optical properties can be obtained when Bi2O3≥50mol%.