Yb3+-concentration-dependent upconversion luminescence of Ho3+-Yb3+ codoped La9.31(Si1.04O4)6O2 for optical thermometer

A series of La9.31(1-x)(Si1.04O4)(6)O-2:1%Ho3+,xYb(3+) (LS:1%Ho3+,xYb(3+), 0 <= x <= 20%) phosphors were synthesized by a solid-state reaction process. The structure and morphology of the samples were investigated by XRD, SEM, TEM, etc. Under the excitation of 980 nm, the LS:Ho3+,Yb3+ exhibited strong red emission and weak green emission. The intensities of the two UC emissions varied differently with the increase of Yb3+ concentration, which was interpreted by possible cross-relaxations. And, the cross-relaxation processes were verified from the decreasing decay lifetimes of Ho3+ with the increase of Yb3+ concentration. Importantly, based on the fluorescence intensity ratio (FIR) technique, the temperature sensing properties in the system were characterized in the temperature range of 283-523 K. The different change rates of the green and red emission intensities with temperature were explained by using the decay lifetimes at various temperature. The S-A value of LS:1% Ho3+,10%Yb3+ reached 0.0551 K--(1) in the wide temperature range from 298 to 548 K. The above investigation results indicated that the LS:Ho3+,Yb3+ phosphors may be potential candidates for optical temperature sensor.

Automated summary

A series of LS:1%Ho3+,xYb(3+) phosphors with different Yb3+ concentrations were synthesized and characterized. The samples exhibited strong red emission and weak green emission under excitation of 980 nm. The intensity of the UC emissions varied with the increase of Yb3+ concentration. The temperature sensing properties of LS:Ho3+,Yb3+ were characterized using the fluorescence intensity ratio technique.