Constructing high sensitivity thermometry with dual-emitting Nd3+/Er3+/Yb3+ codoped BaWO4 single crystal material

Optimizing optical thermometry with tri-doped Ba2GdV3O11 phosphors: Ratiometric and fluorescence lifetime analysis

Optical sensor technology has undergone a transformative evolution with the advent of fluorescence ratio techniques (FIR) and fluorescence lifetime (FL) strategies, revolutionizing precision, performance, and reliability. This study delves into the synthesis of Ba2GdV3O11 phosphors doped with Ho3+/Nd3+, Er3+, and Yb3+, employing the sol-gel method for upconverting material fabrication. A thorough investigation into the structural, morphological, and optical properties of the synthesized phosphors is conducted. Excitation at 980 nm unveils upconversion (UC) emissions across green and red spectra. The intensities of the observed emission bands for Ho3+, Nd3+, and Er3+ demonstrate significant sensitivity to fluctuations in temperature. Temperature sensing relies on the 4S3/2 and 2H11/2 upconversion emissions bands, in addition to the emission lifetimes at 4S3/2. Enhanced thermal sensitivity values are attained, reaching up to 1.03 % K-1 and 1.07 % K-1 using the FIR strategy, and up to 0.146 % K-1 and 0.47 % K-1 with the FL strategy for Ho3+/Er3+/Yb3+ and Nd3+/Er3+/Yb3+ tri-doped Ba2GdV3O11 phosphors, respectively. Furthermore, the studied phosphors exhibit remarkable precision in detecting minute temperature changes (0.3 K), positioning them as promising candidates for precise temperature sensing. This study pioneers innovative methodologies to advance optical thermometry techniques, offering promising prospects for scientific and industrial applications reliant on precise optical temperature sensing.

Investigation on anomalous thermal enhancement and temperature sensing properties of Zn3Mo2O9:Yb3+/RE3+ (RE = Er/Ho) phosphors

In this work, Yb³⁺/RE³⁺ (RE = Er/Ho) co-doped Zn₃Mo₂O₉ phosphors were synthesized by high-temperature solid-state reactions. Under 980 nm excitation, the upconversion (UC) luminescence thermal enhancement was obtained for Zn₃Mo₂O₉:Yb³⁺/RE³⁺ phosphors. The green emission intensity of the Zn₃Mo₂O₉:Yb³⁺/Er³⁺ sample was increased 5 times from 373 to 573 K. The red emission intensity of the Zn₃Mo₂O₉:Yb³⁺/Ho³⁺ sample was enhanced 7.92 times. The anomalous thermal enhancement of UC emission was induced by the negative thermal expansion (NTE) of the Zn₃Mo₂O₉ host. The energy transfer rate from the sensitizer (Yb³⁺) to the activator (RE³⁺) was enhanced because of the lattice contraction and distortion for NTE materials. Compared with the UC emission of Er³⁺single doped Zn₃Mo₂O₉ sample, the luminescence thermal enhancement was absent, which contributed to proving the physical mechanism. The temperature sensing properties of the Zn₃Mo₂O₉:Yb³⁺/Er³⁺ and Zn₃Mo₂O₉:Yb³⁺/Ho³⁺ samples were also investigated based on the fluorescence intensity ratio (FIR) technology. The absolute sensitivity (S_A) and relative sensitivity (S_R) of Zn₃Mo₂O₉:Yb³⁺/Er³⁺ phosphor reached 0.0060 K^-1 and 0.72% K^-1, which is based on the thermal coupling levels (²H_11/2, ⁴S_3/2) FIR of Er³⁺ ions. In addition, the S_A and S_R of Zn₃Mo₂O₉:Yb³⁺/Ho³⁺ phosphor reached 0.0119 K^-1 and 0.86% K^-1, that is based on the non-thermal coupling levels (⁵S₂/⁵F₄, ⁵F₅) FIR of Ho³⁺ ions. The research results indicate that the Zn₃Mo₂O₉ host shows NET. The Yb³⁺/RE³⁺ co-doped Zn₃Mo₂O₉ phosphors are good materials for highly sensitive optical temperature measurement, which can be used to develop thermally enhanced ratiometric optical thermometers.