Luminescent GeO2–Pb–Bi2O3 glasses co-doped with Tb3+1 and Eu3+: Excitation energy transfer and color chromaticity

• Heavy metal glass of the type GeO2–PbO–Bi2O3 doped with Eu3+ and Tb3+ was prepared.
• IR spectra suggested presence of tetrahedral [GeO4] as well as octahedral [GeO6] and [BiO6] structural units in the glass.
• In the glassy matrix appeared such effects as energy transfer Tb[3+] → Eu[3+] and cross-relaxation Tb3+ → Tb3+.
• Increase of the Eu[3+] content at the cost of Tb3+ changed emission color of the doped glass from cool white to red.

Heavy metal oxide glass of the type GeO2–PbO–Bi2O3 was applied as a matrix for luminescent materials co-doped with Tb3+ and Eu3+ ions of different molar ratio. The undoped glass matrix with the composition 80GeO2–19PbO–1Bi2O3 was characterized by XRD and DSC techniques. Its structure was studied by FTIR spectroscopy. The FTIR spectra suggested that GeO4, GeO6, BiO3, BiO6, PbO3 and PbO4 structural units are present in the glass. In the case of the 79GeO2–19PbO–Bi2O3–xEu2O3–(1 − x)Tb2O3 luminescent glasses, reflection, luminescence and excitation spectra were recorded as well as time resolved luminescence technique was used. Two luminescence effects were analyzed, viz. cross relaxation and Tb3+ → Eu3+ energy transfer.