Insight into Eu 3+ -Doped Phase-Change K 3 Lu(PO 4 ) 2 Phosphate toward Data Encryption

Adjusting the local coordination environment of lanthanide luminescent ions can modulate their crystal-field splittings and broaden their applications in the relevant optical fields. Here, we introduced Eu ions into the phase-change K Lu(PO ) phosphate and found that the temperature-induced reversible phase transitions of K Lu(PO ) (phase I ⇆ phase II and phase II ⇆ phase III, below room temperature) give rise to an obvious photoluminescence (PL) difference of Eu ions. The Eu emission mainly focused on the D → F transition in phase III but manifested comparable D → F transitions in the two low-temperature phases. On this basis, the change of Eu -doped concentration led to the phase evolution in Eu :K Lu(PO ) , which could stabilize two types of low-temperature polymorphs to the specific temperature by controlling the doping content. Finally, we proposed a feasible information encryption strategy based on the PL modulation of Eu :K Lu(PO ) phosphors, which was caused by the temperature hysteresis of the relevant phase transition, exhibiting good stability and reproducibility. Our findings pave an avenue for exploring the optical application of lanthanide-based luminescent materials by introducing phase-change hosts.