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

A series of La 9.31(1-x) (Si 1.04 O 4 ) 6 O 2 :1%Ho 3+ ,xYb 3+ (LS:1%Ho 3+ ,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:Ho 3+ ,Yb 3+ exhibited strong red emission and weak green emission. The intensities of the two UC emissions varied differently with the increase of Yb 3+ concentration, which was interpreted by possible cross-relaxations. And, the cross-relaxation processes were verified from the decreasing decay lifetimes of Ho 3+ with the increase of Yb 3+ 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%Ho 3+ ,10%Yb 3+ reached 0.0551 K -1 in the wide temperature range from 298 to 548 K. The above investigation results indicated that the LS:Ho 3+ ,Yb 3+ phosphors may be potential candidates for optical temperature sensor. • The upconversion luminescence characteristics of LS:Ho 3+ ,Yb 3+ were studied. • High sensitivity for optical temperature-sensing was found in the phosphors. • The present phosphors could be promising in optical temperature sensing.