Optical properties of lead diborate glass ceramics doped with Ce and Eu

Abstract

Glass ceramics of PbB4O7 doped with 0.15 and 0.50% molar concentration of Ce and Eu were prepared by means of controlled crystallization of the glass powder. Crystallization was carried out at 590°C for the undoped and at 640°C for the doped glass ceramic samples. Heat treatment time was 60 and 180min for both kinds of samples. Crystalline phase analysis reveals that the only present phase was lead diborate. Thermal analysis characterization shows that Europium may act as nucleation promoter, lowering the energy barrier for crystallization. On the other hand Cerium acts as inhibitor of the crystallization process. Optical characterization was done by means of absorption spectroscopy and luminescence measurements at room temperature. A shift in absorption edges was observed for both samples; this shift could be attributed to a large amount of BO4 groups as dopant concentration increases. From the luminescence spectra it was showed that the 5D0 to 7F2 red emission (613nm) occurs through an electric dipole mechanism which is dominant in all the Europium doped samples, while in Cerium doped samples the emission peaks are due to the 5d–2F5/2 (528nm) and 5d–2F7/2 (472nm) transitions. Thermoluminescence analysis was performed with different irradiation doses (1 and 10Gy) on samples at different concentrations. Results show the incorporation of localized states near the conduction band.