Researchers propose a dual-emission mechanism by co-doping transition metals and rare earth ions

Update time: 2022-09-14

Focusing on the demands for high relative sensitivity of rare earth doped temperature measurement materials, the research team who came from the High Power Laser Unit Technology Laboratory of the Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS) proposed a dual-emission mechanism by co-doping transition metals and rare earth ions. Related research results have been published in Ceramics International on July 31, 2022.

Based on fluorescence intensity ratio technology, lifetime decay temperature measurement, and temperature-dependent empirical formulas such as color coordinate shifts, the research team established a multi-mode self-reference temperature measurement system and realized the detection of Bi3+/Eu3+ co-doped Ca3Y2Ge3O12 crystallites with high relative sensitivity in the temperature range of 297.8-480K and color-tunable luminescence.

The fluorescence intensity ratio technology (FIR) is an effective temperature measurement method among the non-contact optical temperature measurement system. The technology performs temperature monitoring by comparing the relative ratio of the luminescence intensity between two fluorescence peaks, which can significantly reduce the system error caused by excitation source fluctuation, fluorescence loss and other non-temperature factors.

Researchers found that the double emission center co-doped with rare earth ions and transition metal ions exhibits different spectral characteristics based on the electronic configuration and the interaction with surrounding ligands, which can compensate for the narrow band gap of the thermal coupling energy level of rare earth ions in terms of fluorescence intensity ratio thermometry It is beneficial to achieve high relative sensitivity of temperature-sensitive materials.

In this research, the team successfully synthesized Bi3+/Eu3+ co-doped Ca3Y2Ge3O12 crystallites with both color-tunable and temperature measurement capability. The energy transfer mechanism (Bi3+→Eu3+) exhibits tunable polychromatic emission (blue→red) under 285 nm UV excitation. The Bi3+/Eu3+ co-doped Ca3Y2Ge3O12 crystallites based on FIR technology showed a relatively high relative sensitivity value of about 1.9% K-1 at 297.8K, which was higher than other similar matrix materials. The temperature-dependent FIR technology, Eu3+ lifetime technology and color coordinate displacement jointly build a multi-mode synchronous temperature measurement system with self-reference properties.

“This research provides an experimental basis and theoretical guidance for the development of material temperature measurement performance.” ZHANG Hui, a researcher from this team said.

Fig. 1. (a) Temperature-dependent FIR (IBi/IEu) curve. (b) Variation curves of Sa and Sr with temperature based on FIR technique. (c) Sa and Sr curves based on Eu3+ decay lifetime as a function of temperature. (d) The change curve of the color coordinate displacement value corresponding to the temperature. (Image by SIOM)

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WU Xiufeng
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS