Characterization of BGO glass–ceramic materials

Glass–ceramics of the compositions Bi4Ge3O12 (BGO) and Bi2O3–GeO2 have been obtained by pouring molten materials onto graphite plates heated below and above the glass transition temperatures. Glass transitions temperatures have been measured by DSC. Tg is lower in the case of BGO than with the Bi2O3–GeO2 glass ceramics material. Crystallization is evaluated by X-ray diffraction and microscopic observations. The XRD measurements confirm the amorphous structure of the samples cast below Tg. The Hruby factor, which measures the stability of the glass–ceramics, is about 0.21 in the case of BGO glass ceramics suggesting a rather stable glass. The fluorescence under U.V. excitation is larger by one order of magnitude in the case of BGO glass–ceramics by comparison to the Bi2O3–GeO2 glasses, suggesting it is a good candidate for scintillation materials. The images obtained under U.V. excitation shows structured luminescent centers in the case of BGO glass–ceramics.