Investigating the Luminescence Behaviors and Temperature Sensing Properties of Rare-Earth-Doped Ba₂In₂O₅ Phosphors

Abstract

We present a strategy for selecting an optimal material in a particular temperature range by investigating the relationship between the absolute sensitivity ( S_a) and energy gap (Δ E), as well as the relationship between S_a and temperature on the basis of Yb³⁺/Ln³⁺ (Ln = Er³⁺, Ho³⁺)-codoped Ba₂In₂O₅ phosphors. Through an investigation of optical performance, the phosphors exhibit near-infrared (NIR) downshifting and visible upconversion (UC) emissions under 980 nm excitation. The NIR spectral range from 700 to 1800 nm is referred to as the "biological window". The NIR emission peaks of Er³⁺ and Ho³⁺ are located at 1550 nm of the third biological window and 1192 nm of the second biological window, respectively. The temperature sensing behaviors based on the UC luminescence in Yb³⁺/Ln³⁺-codoped Ba₂In₂O₅ phosphors are recorded by the fluorescence intensity ratio (FIR) technique in the temperature range from 303 to 573 K. The Ba₂In₂O₅:Er³⁺/Yb³⁺ sample is usable at temperatures above 350 K, and the Ho³⁺/Yb³⁺-codoped Ba₂In₂O₅ phosphor is suitable at temperatures below 350 K in our experimental region. The above results show that the Ba₂In₂O₅:Ln³⁺/Yb³⁺ phosphors could be promising candidates for optical temperature sensors and applications in the biological imaging field.