Advanced dual-mode Er3+/Yb3+ phosphors for high-precision optical thermometry across broad temperature ranges†

Abstract

Dual-mode light-emitting phosphors play a vital role in advanced technologies and functions as they constitute optical thermometers for a wide range of temperature environments. This study presents a novel Er³⁺/Yb³⁺ co-doped NaCaY(MoO₄)₃ (NCYM) phosphor synthesized via the sol–gel method for precise optical thermometry across a broad temperature range (300–510 K). The research includes an in-depth analysis of the crystal structure, morphology, optical properties, and decay kinetics. The luminescence mechanism and energy transfer processes were elucidated, with NCYM:Er³⁺/Yb³⁺ phosphors efficiently activated under 980 nm and 325 nm laser excitation. These excitations produced ²H_11/2/⁴S_3/2 → ⁴I_15/2 transitions via up-conversion (UC) and down-conversion (DC) mechanisms, respectively. A dual-mode optical thermometry system was developed, combining DC and UC approaches for simultaneous evaluation. At 300 K, the maximum relative sensitivities (S_r-max) were 1.2% K⁻¹ (DC) and 1.045% K⁻¹ (UC), while at 510 K, the maximum absolute sensitivities (S_a-max) reached 15.17 × 10⁻³ K (DC) and 12.15 × 10⁻³ K (UC). The system demonstrated exceptional temperature resolution, with uncertainties (δT) below 0.313 K, covering the full range of 300 to 510 K. This work positions NCYM:Er³⁺/Yb³⁺ phosphors as highly promising materials for precise optical temperature sensing in a variety of advanced applications.