Fig. 1: Phase structure and PL properties of Mg_1-xF₂:xCr³⁺.

a XRD patterns of Mg_1-xF₂:xCr³⁺ (x = 0.1–3.0%). b PL emission spectra of Mg_1-xF₂:xCr³⁺ (x = 0.1–3.0%) under 444 nm excitation, with characteristic Cr³⁺ emissions in R-band (≈700 nm), N-band (≈750 nm) and C-band (>800 nm). c Luminescence decay profiles peaked at 723 nm (top) and 820 nm (bottom) for samples of x = 0.25, 1.0, and 3.0 under 444 nm excitation. Time-resolved PL maps of Mg_2.97F₂:0.03Cr³⁺ under 444 nm excitation within d 0–2 ms and e 2–4 ms, showing dynamic emission evolution over time in the NIR region. The color scale represents intensity on a linear scale. f EPR patterns of Mg_1-xF₂:xCr³⁺ (x = 0.25%, 1.0%, and 3.0%). g Temperature-dependent PL spectra of Mg_2.97F₂:0.03Cr³⁺ under 444 nm excitation from −190 °C to 50 °C. Source data are provided as a Source Data file.