Crystal structure, luminescence properties and thermometric characteristics of Ba2Gd2Ge4O13:Tb3+, Tb3+/Eu3+ germanates
Аннотация
In this work, the synthesis of Ba2Gd2-хTbxGe4O13 (х = 0.05–0.2) and Ba2Gd1.85-yTb0.15EuyGe4O13 (y = 0.1–0.6) solid solutions was carried out for the first time and the crystal structure of the synthesized phases was studied. The XRPD study has verified that all the samples are isostructural to Ba2Gd2Ge4O13 and crystallize in the monoclinic system, S.G. C2/c, Z = 4. The photoluminescence spectra of Ba2Gd2-хTbxGe4O13 germanates consist of a number of lines in the range of 365−650 nm, caused by 5D3,4 → 7FJ transitions in Tb3+ ions. Based on the results of concentration studies, it has been found that Ba2Gd1.85Tb0.15Ge4O13 germanate exhibits the highest emission intensity. This content of Tb3+ (х = 0.15) was fixed and the codoped Ba2Gd1.85-yTb0.15EuyGe4O13 phases were synthesized. Codoping with Eu3+ ions has led to the appearance of additional luminescent lines in the 570−720 nm region, which is associated with 5D0→ 7FJ transitions in europium ions. As the Eu3+ content increases, the color coordinates gradually change, which allows fine-tuning of the emission color of the phosphors. High-temperature studies (T = 298−498 K) were carried out for Ba2Gd1.75Tb0.15Eu0.1Ge4O13 germanate. The temperature dependences of the luminescence of the bands at 530–560 nm (5D4 → 7F5 transition in Tb3+) and 603–640 nm (5D0 → 7F2 transition in Eu3+) as well as LIR = I603-640 nm/I530-560 nm were plotted. The calculated maximum values of absolute and relative sensitivity were 0.34%×K-1 and 0.15%×K-1.
