Fig. 3: Optical properties of SrF₂:Pr³⁺.

a Schematic of experimental procedures for mechanoluminescence (ML) and persistent luminescence (PersL) measurement. b Comparison of spectra of SrF₂:0.5%Pr³⁺ under different conditions. Stage I: obtained before X-ray irradiation. Stage II: obtained immediately after stoppage of 5-min X-ray irradiation. Stage III: obtained upon force stimulation at 5 N after PersL. Stage IV: obtained after thermal bleach. c Repeatability results of trap-controlled ML. d PersL and ML intensity of SrF₂:Pr³⁺ as a function of Pr³⁺ content. e Photographs of visible and UVC PersL of SrF₂:0.5%Pr³⁺, showing progressive changes over time following a 5-min X-ray irradiation. f Photographs of visible and UVC ML of SrF₂:0.5%Pr³⁺@polydimethylsiloxane films stretched under different magnitudes of force. g ML spectra of SrF₂ singly doped with different lanthanides (0.5%mol). Source data are provided as a Source Data file.