Photoluminescence and radioluminescence study of NaMgF3:Eu nanoparticles

•Photoluminescence and radioluminescence in NaMgF3nanoparticles with 0.1%–5% Eu.•Observation of an unidentified defect peak.•Energy transfer between Eu3+ and the defect peak occurs for high Eu concentrations.•No change in the Eu3+ site symmetry for high Eu concentrations.•The radioluminescence is independent of the dose only for low Eu concentrations.

Photoluminescence (PL) and radioluminescence (RL) measurements were made on small (∼25 nm) NaMgF3 nanoparticles doped with Eu concentrations ranging from 0.1% to 5%. We find that they contained Eu3+, Eu2+, and an additional unidentified defect with a broad PL emission ∼470 nm. Similar to previous measurements on larger (57 nm–77 nm) NaMgF3:Eu nanoparticles with 1% Eu and 5% Eu, we find that the PL lifetime decreases with increasing Eu concentration that can be attributed to Eu energy transfer to non-radiative recombination sites. However, there is no change in the fraction of Eu3+ distorted sites. The ∼470 nm PL defect peak was also reported for larger nanoparticles, which suggests that this peak arises from similar unidentified point defects. However, the activated non-radiative decay for the small nanoparticles has a significantly lower activation energy. The Eu3+ RL decreases by only 2.3% at 10 kGy for low Eu concentrations.