Effects of Er3+ concentration on upconversion luminescence and temperature sensing properties in Bi4Ge3O12 crystal

Er3+ doped Bi4Ge3O12(BGO) crystals with different Er3+ ion concentration were prepared by Bridgman-Stockbarge (B-S) method and the temperature dependence of its upconversion (UC) luminescence was investigated systematically. The phases and luminescence properties of all the samples were characterized by X-ray diffraction (XRD) and upconversion luminescence (UCL) spectra. The temperature sensing performance of Er3+ doped Bi4Ge3O12 sample was studied via the fluorescence intensity ratio method from two thermally coupled H-2(11/2) and S-4(3/2) levels. Excited by 980 nm laser, the sensitivity first increased and then decreased with the increase of Er3+ ion concentration, and the maximum sensitivity can be obtained in the 0.3 mol% Er3+ doped sample at 498 K for 50.3 x 10(-4) K-1. Meanwhile, the experiment also proved that Er3+ doped BGO as temperature sensing has a high reliability and repeatability. The influence mechanism of concentration on temperature sensing was studied by using the calculation of the Judd-Ofelt (J-O) theory, 0.3 mol% Er3+ doped Bi4Ge3O12 sample had a larger the ratio of the green radiation transition rate at the thermal coupling level. These results indicated that Er3+ doped Bi4Ge3O12(BGO) crystals may be a good candidate material as optical temperature sensor. (c) 2020 Published by Elsevier B.V.

Automated summary

In this study, Er3+ doped Bi4Ge3O12(BGO) crystals were investigated for their temperature sensing performance, showing that the sensitivity first increased and then decreased with the increase of Er3+ ion concentration, with the maximum sensitivity achieved in the 0.3 mol% Er3+ doped sample. The calculation using the Judd-Ofelt (J-O) theory revealed a larger ratio of green radiation transition rate at the thermal coupling level in the 0.3 mol% Er3+ doped Bi4Ge3O12 sample, suggesting it as a good candidate material for optical temperature sensing.