Effect of dopant contents on upconversion luminescence and temperature sensing behavior in Ca3La6Si6O24:Yb3+-Er3+/Ho3+ phosphors

Abstract At present, improving the sensitivity is one main object for optical temperature sensing. In this work, a series of Yb 3+ -Er 3+ and Yb 3+ -Ho 3+ doped Ca 3 La 6 Si 6 O 24 (CLS) phosphors were designed by solid-state reaction method to develop new rare earth (RE) ions activated upconversion luminescence materials based on thermally coupled and non-thermally coupled levels of Er 3+ /Ho 3+ . For the CLS:0.6Yb 3+ ,xEr 3+ (0.03 ≤ x ≤ 0.18) and CLS:yYb 3+ ,0.03Er 3+ (0.3 ≤ y ≤ 1.2) samples, the relative intensities of Er 3+ different emission peaks change with the RE ions concentrations, which was interpreted by the proposed cross-relaxation (CR) processes. For the CLS:0.6Yb 3+ ,mHo 3+ (0.03 ≤ m ≤ 0.18) and CLS:nYb 3+ ,0.03Ho 3+ (0.3 ≤ n ≤ 1.2) samples, the 5 F 5 - 5 I 8 transition intensity of Ho 3+ shows a continuous decrease with increasing Yb 3+ or Ho 3+ concentrations by normalizing the ( 5 F 4 , 5 S 2 )- 5 I 8 transition of Ho 3+ , which was explained by the CR between Yb 3+ and Ho 3+ . The temperature dependence of the fluorescence intensity ratio for Er 3+ and Ho 3+ emissions was discussed in detail. The relative and absolute sensitivities were compared by using thermally coupled and non-thermally coupled levels of Er 3+ and Ho 3+ . The present investigation could be instructive to develop new luminescent materials with high sensitivity.