Crystal structure, morphology and enhancement of luminescence properties of Cr3+-doped KZnF3 phosphor by using a HF-free hydrothermal method with different chromium sources

In this study, a series of near-infrared (NIR) KZnF _3 :Cr ^3+ phosphors was prepared by different chromium sources using a HF-free hydrothermal method. The influence of different chromium sources on the crystal structure, morphology, and luminescence properties of Cr ^3+ -doped KZnF _3 phosphors were systematically investigated. The results showed that the chromium source changed from CrF _3 ·xH _2 O to (NH _4 ) _3 CrF _6 and leaded to an increased crystal field, resulting in a blue shift of the emission peak position from 803 nm to 753 nm, accompanied by the full-width half maximum (FWHM) reduced from 140 nm to 122 nm. Moreover, KZnF _3 :0.03Cr ^3+ (CrF _3 ·xH _2 O) and KZnF _3 :0.03Cr ^3+ ((NH _4 ) _3 CrF _6 ) phosphors maintained 58% and 87% of their initial room-temperature intensity at 423 K, respectively. These results indicated that altering the synthetic raw materials provided new insights for designing NIR phosphors with highly thermal stability.