White emitting phosphors based on glasses of the type 10AlF3–10TiO2–39PbO–30H3BO3–10SiO2–xEu2O3–(1−x)Tb2O3: An energy transfer study

Abstract

Glasses consisting of heavy metal oxides, a metal fluoride and two lanthanoid oxides (as dopants) of the type 10AlF3–10TiO2–39PbO–30H3BO3–10SiO2–xEu2O3–(1−x)Tb2O3 were prepared as phosphors with different molar ratio x. The un-doped matrix glass was characterized by XRD and DSC techniques. Its structure was also studied by FTIR techniques that suggested the presence of B–O−, B–Ø–B, Pb–O, Al–Ø–B and Al–O− bonds as well as [BO3]3−, [BØO3], [BØ4], and [SiØ4] structural units as well as Ln–O–Ln clusters. For the Eu3+ and Tb3+ co-doped luminescent glasses optical absorption, luminescence and excitation spectra were recorded as well as time resolved luminescence techniques was used. Two luminescence effects were analyzed, viz. cross-relaxation Tb3+→Tb3+ energy transfer and Tb3+→Eu3+ energy transfer. The CIE diagram suggests that especially the glass co-doped with Eu3+ and Tb3+ in molar ratio x=0.5 can be recognized as a cold white phosphor.