Novel IR Phosphor Based on Sr3La2(Ge3O9)2 : Nd3+,Ho3+ Germanate

Cyclogermanate Sr3La2(Ge3O9)2, isostructural to silicate Sr3Er2(Si3O9)2, activated by neodymium and holmium is obtained for the first time by the precursor method. Ion Nd3+ in the structure of Sr3La2(Ge3O9)2 is a sensitizer of the infrared luminescence of Ho3+. Excitation by radiation with a wavelength of 808 nm leads to a series of emission lines in the luminescence spectra of Sr3La2-xNd x (Ge3O9)2 : Ho3+ in the short-wave and middle-IR ranges (1.0–3.4 μm). The highest intensity of lines at 2.1 and 2.7 μm, associated with the 5I7 → 5I8 and 5I6 → 5I7 transitions in the Ho3+ ion, is found for compositions containing traces of holmium. Based on the analysis of the concentration dependences of the luminescence intensity, an optimal composition of the phosphor is determined, which ensures the maximum efficiency of conversion of laser radiation energy. The data obtained are interpreted in the assumption of cross-relaxation energy transfer from Nd3+ to Ho3+.