Upconversion luminescence of germanate nanophosphors activated by Er3+ and Yb3+ ions

The crystallophores of the composition Sr2La8(1x-y)ErxYbyGe6O26 (x = 0.01, 0.05, 0.075, 0.1, 0.15) were synthesized. Nanophosphores in the amorphous state were obtained for the first time by the method of pulsed electron beam evaporation using a phosphor of the composition Sr2La7.85Er0.075Yb0.075Ge6O26 with the structure of oxyapatites as a target. DSC-TGA analysis was performed to determine the temperature stability and the onset of crystallization of the nanosample. A change in the Raman spectra of the samples with a decrease in the particle dimension from the bulk to nanoscale state was found. The spectral characteristics of the upconversion photoluminescence of samples in polycrystalline and nano-amorphous states are studied. It has been shown that luminescence is influenced by nonradiative processes between different transitions of Er3+ ions. There is a threshold population of the Er3+ and Yb3+ levels (level 2F5/2) in the region of relatively low pumping powers of nanosamples by laser radiation with a wavelength of λex = 980 nm. Above this threshold a sharp increase in the intensity of upconversion photoluminescence occurs.