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Bismuth borate glasses with Bi(2)O(3) concentration of 20-66 mol% were prepared by melt quenching and devitrified by heat treatment above their glass transition temperatures. All glasses show a strong tendency towards crystallization on annealing that increases with Bi(2)O(3) concentration. The crystalline phases formed on devitrification were characterized by FTIR absorption spectroscopy and DSC measurements. Our studies reveal that phases produced in glasses are strongly determined by initial glass composition and the two most stable crystalline phases are: Bi(3)B(5)O(12) and Bi(4)B(2)O(9). The metastable BiBO(3) phase can also be formed by devitrification of glass with 50 mol% of Bi(2)O(3). This phase is, however, unstable and decomposes into Bi(3)B(5)O(12) and Bi(4)B(2)O(9) on prolonged heat treatment.

Bismuth borate glasses from the system: 40Bi2O3–59B2O3–1Tv2O3 (where Tv=Al, Y, Nd, Sm, and Eu) and three glasses of composition: 40Bi2O3–60B2O3, 37.5Bi2O3–62.5B2O3 and 38Bi2O3–60B2O3–2Al2O3 were prepared by melt quenching and characterized by density, UV‐visible absorption spectroscopy and differential thermal analysis (DTA) studies. Bismuth borate glasses exhibit a very strong optical absorption band just below their absorption edge. Glasses were devitrified by heat treatment at temperatures above their glass transition temperatures and the crystalline phases produced in them were characterized by Fourier transform infrared (FTIR) absorption spectroscopy and X‐ray diffraction (XRD). Bi3B5O12 was found to be the most abundant phase in all devitrified samples. DTA studies on glasses and FTIR and XRD analysis on crystallized samples revealed that very small amounts of trivalent ion doping causes significant changes in the devitrification properties of bismuth borate glasses; rare‐earth ions promote the formation of metastable BiBO3–I and BiBO3–II phases during glass crystallization.

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