K3LaTe2O9:Er: a novel green up-conversion luminescence material

Abstract

A novel green up-conversion luminescence material, K₃LaTe₂O₉:Er, was synthesised via a solid-state reaction method. K₃LaTe₂O₉:Er phosphors were characterised by X-ray diffraction, reflectance spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, up-conversion spectroscopy and temperature sensing performance analysis. The diffraction pattern of the hexagonal K₃LaTe₂O₉:0.02Er microcrystals was indexed with Miller indices and the lattice constants were a = b = 0.60636 ± 0.00018 nm, and c = 1.49543 ± 0.00037 nm. The photoluminescence under 380 nm excitation and the up-conversion luminescence under 980 and 1550 nm pumping were investigated. The influence of Er³⁺ ion concentration and excitation power on the luminescence properties of K₃LaTe₂O₉:Er was also discussed. K₃LaTe₂O₉:Er phosphor presented green down-shifting emission and up-conversion luminescence under 380, and 980 nm excitation and yellow–green up-conversion luminescence under 1550 nm pumping, respectively, and the red emission component was enhanced with the increment in excitation wavelength. The quenching concentration of Er³⁺ ions in K₃LaTe₂O₉:Er was much higher than that in normal phosphors. This result can be attributed to the suppression of energy migration because the shortest (0.606 nm) and average distance (0.9720 nm) between Er³⁺ ions were significantly large in K₃LaTe₂O₉. Therefore, the electric quadrupole–quadrupole interactions between Er³⁺ ions are the dominant energy transfer process in down-shift emission, and the UCL mechanism can be regarded as the excited state absorption in K₃LaTe₂O₉:Er. Furthermore, the doping concentration of Er³⁺ ions influenced the temperature sensitivity of K₃LaTe₂O₉:Er.