Effects of optical-inert ions on upconversion luminescence and temperature sensing properties of ScVO4:10%Yb3+/2%Er3+ nano/micro-particles

In this paper, ScVO4:10%Yb3+/2%Er3+ nano/micro-particles doped with optical-inert metal ions including the alkali metal ions (Li+/Na+/K+), alkaline-earth metal ions (Mg2+/Ca2+/Sr2+/Ba2+) and lanthanide ions (Y3+/Gd3+/Lu3+) were synthesized by a conventional solid-state method. X-ray diffraction studies show that the prepared ScVO4:10%Yb3+/2%Er3+ whether single-doping, codoping or tridoping optical-inert metal ions are highly crystalline in nature with tetragonal phase structure when the doping concentration <= 10%. Under a 980 nm laser diode excitation, the upconversion luminescence was enhanced significantly by single doping of Li+, Na+, K+, Mg2+, Ca2+, Sr2+, Ba2+, Y3+, Gd3+ or Lu3+, showing the strongest green emission with 5 mol% Li+ dopant. For codoping optical-inert metal ions system, it is found that Li+/Gd3+ couple is the most effective codopant, leading to an drastic increase of the UC luminescence centered at 554 nm by a factor of 15.3 compared to optical-inert metal ions free sample, while the factor of Li+/Ca2+/Gd3+ tridoping system is only 4.6. This work aims to investigate the origin of UC luminescence enhancement for ScVO4:10%Yb3+/2%Er3+ after codoping optical-inert ions based on the systematical analyses of the structures, morphologies, chemical states of elements, oxygen defects, optical absorption properties, etc. Furthermore, temperature-sensing performance was also investigated using the fluorescence intensity ratio technique. This opens a new window for studying the cooperation of the optical-inert ions doping effect on improving UC luminescence and temperature sensitivity properties.