A High‐Throughput Screening Discovered Dual‐Emissive Li 2 HfF 6 :Mn 4 + for Fiber‐Optic Temperature Sensing

Fluorescence intensity ratio (FIR)‐based optical fiber temperature sensors are highly favored due to their immunity to electromagnetic interference and durability in harsh environments. However, the development of such sensors is often hindered by severe spectral overlap in dual‐site‐doped transition‐metal systems. This study employs high‐throughput screening of 10 480 fluorides to theoretically predict and identify Li 2 HfF 6 as an ideal host. The calculated wavelength difference of 5.21 nm effectively suppresses the overlap of dual‐site Mn 4+ emissions. This theoretical prediction is experimentally validated, showing that Mn 4+ occupation at two distinct octahedral sites produces sharp and well‐resolved emission peaks with a 5 nm wavelength difference. The synthesized Li 2 HfF 6 :Mn 4+ phosphor exhibits significantly different thermal quenching behaviors at the two sites, resulting in a highly linear and sensitive FIR temperature dependence in the range of 260–330 K. The absolute and relative sensitivities reach 0.0051 K −1 and 1.3% K −1 , respectively. Based on this material, an all‐optical‐fiber temperature sensing probe is further developed, achieving high‐precision temperature measurement (maximum uncertainty < 0.5°C) within 0°C–40°C. This work provides a rational design strategy from theoretical prediction to device application, offering a solution to the spectral overlap challenge in transition metal dual‐site systems.