Multi-site Cr3+ occupation-related broadband NIR luminescence in Cr3+-doped Li3Mg2NbO6

Broadband near-infrared (NIR) luminescent materials have recently attracted significant attention as advanced smart optical sources for NIR spectroscopy. In this work, a broadband NIR emission from 650 nm to 950 nm with a full width at half maximum up to 160 nm was acquired in a Cr3+-activated Li3Mg2NbO6 phosphor under blue excitation. Based on the structural simulation and spectral characteristic analysis, this broad spectrum is inferred to be composed of emissions from Cr3+ substituting three different crystallographic sites with different crystal field environments. The temperature-dependent luminescence properties of Li3Mg2NbO6:Cr3+ were revealed to be multiple thermal processes related to the multi-site occupation behaviors of Cr3+ ions in the host. A 10 mW NIR output was achieved from the phosphor-converted LEDs fabricated by the as-prepared Li3Mg2NbO6:Cr3+ phosphor and blue InGaN chip. The obtained results have offered significant insight into exploring novel transition metal ion-based broadband NIR materials for phosphor-converted LEDs.