Realizing Antithermal Quenching Red Emission in Mn4+-Activated Rb2NaVF6 for Optical Thermometry Sensor Application

Currently, the development of red Mn4+-activated fluoride luminescent materials attracts a lot of attention in optical thermometry sensors, solid lighting, display, and plant growth areas. Nevertheless, the thermal stability of Mn4+-activated fluoride luminescent materials is still a crucial issue. Herein, a new red Rb2NaVF6:Mn4+ luminescent material with outstanding thermal stability was successfully synthesized through the facial coprecipitation method. Mn4+ ions prefer to occupy VF6 octahedra based on the accurate Rietveld refinement results. Accordingly, the as-prepared Rb2NaVF6:Mn4+ exhibits a broad absorption region from 300 to 500 nm with a maximum of 468 nm, matching well with the near-ultraviolet and blue InGaN chip. Upon 468 nm excitation, Rb2NaVF6:Mn4+ can emit narrow-band red light at 632 nm. Notably, Rb2NaVF6:Mn4+ shows superior antithermal quenching properties, of which the integrated intensities at 175 degrees C can realize as high as 140% than that at 25 degrees C. Owing to the diverse thermal quenching behavior between anti-Stokes and Stokes emission, Rb2NaVF6:Mn4+ displays promising candidates in optical thermometry sensors with a relative sensitivity Sr of 0.49%. This study offers new insight into developing antithermal quenching red Mn4+-activated fluoride luminescent materials.