Optical temperature sensing with an Er3+, Yb3+ co-doped LaBMoO6 single crystal

Abstract

Optical temperature sensing technology, especially the fluorescence intensity ratio (FIR) type sensor based on Er³⁺, Yb³⁺ co-doped up-conversion (UC) luminescent materials, presents numerous opportunities in the field of temperature detection. Various Er³⁺, Yb³⁺ co-doped fluorides and oxides have been explored for the application of temperature sensing. Most of these Er³⁺, Yb³⁺ co-doped sensing materials are phosphors, for which the high temperature phase and chemical stability is still challenging. The Er³⁺, Yb³⁺ co-doped oxide single crystal is a promising solution to explore temperature sensing materials with practical application ability. In this work, an Er³⁺, Yb³⁺ co-doped LaBMoO₆ single crystal (LBMO-SC: Er³⁺, Yb³⁺) is grown through flux assisted spontaneous crystal growth technology. Compared with the Er³⁺, Yb³⁺ co-doped LaBMoO₆ polycrystalline samples (LBMO-PC: Er³⁺, Yb³⁺), the LBMO-SC: Er³⁺, Yb³⁺ shows improved UC performance with enhanced light emission and prolonged luminescence lifetime. The UC performance improvement results from the more efficient energy transfer between Yb³⁺ and Er³⁺. The energy transfer efficiency from Yb³⁺ to Er³⁺ in the LBMO-PC: Er³⁺, Yb³⁺ powders sintered at 1000 °C for 15 h is 7.3%, while it is 29.7% in the LBMO-SC: Er³⁺, Yb³⁺. The strong UC luminescence of LBMO-SC: Er³⁺, Yb³⁺ extends the temperature detection range; the luminescence of ⁴S_3/2 → ⁴I_15/2 in LBMO-SC: Er³⁺, Yb³⁺ is still measurable even when the temperature reaches 570 K. The LBMO-SC: Er³⁺, Yb³⁺ has a maximum value of relative temperature sensitivity of 1.16% K⁻¹ at 300 K. Finally, an optical fiber type temperature sensor with practical application capability is successfully fabricated by using LBMO-SC: Er³⁺, Yb³⁺ as the luminescence sensing medium.