Up-conversion luminescence properties and energy transfer mechanism of SrAl2B2O7: Er3+@Yb3+ phosphors

The Er 3+ @Yb 3+ co-doped SrAl 2 B 2 O 7 phosphors were prepared by a sol-gel auto-combustion method. The components, microstructure and up-conversion (UC) properties of samples were investigated systematically. The phosphors emitted red light and green light under the excitation of 980 nm wavelength. The intensity of red emission and green emission nearly linearly decreased with increasing ambient temperatures. The red emission, green emission and their intensity ratio as a function of Er 3+ concentrations and Yb 3+ concentrations were studied in detail. The results show that 4.0% Er 3+ and 8.0% Yb 3+ doped samples can obtain the best luminescence intensity while the best light purity cannot be obtained simultaneously. The intensity of red and green emission was measured as a function of excitation power. It indicates that there was no photon avalanche mechanism for SrAl 2 B 2 O 7 : Er 3+ @Yb 3+ due to the absence of sharp change of n values. The UC luminescence corresponded to a two-photon absorption process which was illustrated by the energy transfer mechanism and the steady-state rate equations. Because of the controllable monochromatic luminescence and excellent temperature-dependent luminescence properties, the SrAl 2 B 2 O 7 : Er 3+ @Yb 3+ phosphors have potential application in the fields of non-contact temperature measurement and bio-polychromatic label.