Visualized real-time flexible high-temperature sensing in Eu3+/Tb3+-doped Y2Mo3O12 negative thermal expansion material films

Abstract

The demand for accurate temperature readings in harsh high-temperature environments includes miniaturization, flexibility, visualization, and integrability of temperature sensors with the growing need for human development. Rare earth-doped non-contact fluorescence intensity ratio (FIR) temperature sensors have received widespread attention due to their high detection accuracy and fast response ability. However, the limitations of thermal quenching (TQ) and thermal coupling energy level differences restrict their applications. In this work, a novel temperature sensing method in Eu³⁺/Tb³⁺-doped Y₂Mo₃O₁₂ negative thermal expansion (NTE) materials is proposed, which depends on different energy transfer characteristics of Eu³⁺- and Tb³⁺-doped NTE materials. Under a 295 nm excitation laser, the Y₂Mo₃O₁₂:Eu³⁺ phosphor achieved 600% enhancement due to the charge-transfer band (CTB) absorption between O²⁻ and MoO₄²⁻. At 573 K, the luminescence intensity of Y₂Mo₃O₁₂:Tb³⁺ is reduced by 30 times due to the absence of energy transfer between the Tb³⁺ ions and Y₂Mo₃O₁₂ NTE materials. The Y₂Mo₃O₁₂:Eu³⁺/Tb³⁺ mixing materials enhance the relative luminescence intensity and solve the thermal coupling energy level differences, achieving high sensitivity and resolution (maximum S_r = 2.56% K⁻¹ at 453 K). The Y₂Mo₃O₁₂:Eu³⁺/Tb³⁺ flexible thin film achieves multiple naked-eye color spans, breaking free from the limitations of optical detection instruments and demonstrating strong potential for robust and direct temperature reading without equipment. This demonstrates their superior advantages for visualizing real-time high-temperature sensing with nonplanar surfaces, thermal defect diagnosis systems, intelligent battery monitoring systems, and other high-temperature sensing fields.