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

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.