Photoluminescence of Eu3+-, Tb3+-, Dy3+- and Tm3+-doped transparent GeO2-TiO2-K2O glass ceramics

In this paper, we present the photoluminescence properties of Eu3+-, Tb3+-, Dy3+- and Tm3+-doped potassium-titanium-germanate glasses and glass ceramics. Following the x-ray diffraction measurement, the glass structure was established. Compared to Eu3+-, Tb3+-, Dy3+- and Tm3+-doped glasses, their respective glass ceramics show stronger emissions due to the presence of the K2TiGe3O9 crystalline phase. For Eu3+-doped glass and glass ceramics, five emission bands centered at 578 nm (D-5(0) -> F-7(0)), 592 nm (D-5(0) -> F-7(1)), 614 nm (D-5(0) -> F-7(2)), 653 nm (D-5(0) -> F-7(3)) and 702 nm (D-5(0) -> F-7(4)) have been observed with 394 nm (D-5(0) -> L-7(6)) excitation wavelength. Of them, 614 nm (D-5(0) -> F-7(2)) has shown a bright reddish-orange emission. For Tb3+-doped glass and glass ceramic, four emission bands centered at 490 nm (D-5(4) -> F-7(6)), 549 nm (D-5(4) -> F-7(5)), 586 nm (D-5(4) -> F-7(4)) and 621 nm (D-5(4) -> F-7(3)) have been observed with an excitation at 378 nm (F-3(6) -> (5)G(6)) wavelength. Of them, 549 nm (D-5(4) -> F-7(5)) has shown a bright green emission. With regard to Dy3+: glass and glass ceramic, a blue emission band centered at 485 nm (F-4(9/2) -> H-6(15/2)) and a bright fluorescent yellow emission at 576 nm (F-4(9/2) -> H-6(13/2)) have been observed, apart from F-4(9/2) -> H-6(11/2) (665 nm) emission transition with an excitation at 387 nm (H-6(15/2) -> I-4(13/2), F-4(7/2)) wavelength. Emission bands of (1)G(4) -> F-3(4) (650 nm) and F-3(3) -> H-3(6) (700 nm) transitions for the Tm3+: glass and glass ceramic, with excitation at H-3(6) -> (1)G(4) (468 nm), have been observed. The stimulated emission cross sections of all the emission bands of Eu3+, Tb3+, Dy3+ and Tm3+: glasses and glass ceramics have been computed based on their measured Delta lambda (FWHM) and lifetimes (tau(m)).