Insight into Eu³⁺-Doped Phase-Change K₃Lu(PO₄)₂ Phosphate toward Data Encryption

As for Eu3+:K3Lu(PO4)(2), the Eu3+ ions amongthe three phases manifesta dramatic luminescence distinction due to the difference in the relevantlocal coordination environment. The variation of Eu3+-dopedconcentration led to polymorphic evolution in Eu3+:K3Lu(PO4)(2), which shows an obvious photoluminescencehysteresis during the heating and cooling processes. On that basis,a feasible information encryption strategy was proposed. Our findingsopen up a new route for developing lanthanide-based information encryptionbased on the phase-change hosts. Adjusting the local coordination environment of lanthanideluminescentions can modulate their crystal-field splittings and broaden theirapplications in the relevant optical fields. Here, we introduced Eu3+ ions into the phase-change K3Lu(PO4)(2) phosphate and found that the temperature-induced reversiblephase transitions of K3Lu(PO4)(2) (phaseI ? phase II and phase II ? phase III, below room temperature)give rise to an obvious photoluminescence (PL) difference of Eu3+ ions. The Eu3+ emission mainly focused on the D-5(0) -> F-7(1) transitionin phase III but manifested comparable D-5(0) -> F-7(1,2) transitions in the two low-temperature phases.On this basis, the change of Eu3+-doped concentration ledto the phase evolution in Eu3+:K3Lu(PO4)(2), which could stabilize two types of low-temperaturepolymorphs to the specific temperature by controlling the doping content.Finally, we proposed a feasible information encryption strategy basedon the PL modulation of Eu3+:K3Lu(PO4)(2) phosphors, which was caused by the temperature hysteresisof the relevant phase transition, exhibiting good stability and reproducibility.Our findings pave an avenue for exploring the optical applicationof lanthanide-based luminescent materials by introducing phase-changehosts.