Glass composition dependence of luminescence due to Ge2+ center in germanate glasses

Abstract Germanate glasses were prepared by the melt-quenching method using an assembled hot-thermocoupler equipped in a sample chamber of a fluorescence spectrometer, and subsequently their luminescence and excitation spectra were measured. In the GeO 2 glass, luminescence bands due to the Ge 2+ center appeared at the central wavelengths of 300 and 395 nm, their excitation bands being at 250 and 330 nm, respectively. In the (100 − x )GeO 2 − x M m O n glasses, for M m O n = B 2 O 3 ( x ≦ 50), SiO 2 ( x ≦ 40), and Al 2 O 3 ( x ≦ 2), the luminescence intensity and therefore the amount of the Ge 2+ center increased with increasing the content of M m O n , where M (2 n / m )+ ions (B 3+ , Si 4+ , and Al 3+ ) have lower basicities than a Ge 4+ ion. Contrarily, for M m O n = Li 2 O ( x ≦ 30), Na 2 O ( x ≦ 20), K 2 O ( x ≦ 20), CaO ( x ≦ 20), SrO ( x ≦ 3), BaO ( x ≦ 15), ZnO ( x ≦ 20), Ga 2 O 3 ( x ≦ 10), Sb 2 O 3 ( x ≦ 20), Bi 2 O 3 (15 ≦ x ≦ 25), TiO 2 ( x ≦ 3), and Nb 2 O 5 ( x ≦ 10), the luminescence intensity and the amount of the Ge 2+ center rapidly decreased with increasing the amount of additives and disappeared, where M (2 n / m )+ ions (Li + , Na + , K + , Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , Ga 3+ , Sb 3+ , Bi 3+ , Ti 4+ , and Nb 5+ ) have higher basicities than a Ge 4+ ion.