Enhancing the Photoluminescence Property of Pr³⁺ Ions by Understanding the Polymorphous Influence of the K₃Lu(PO₄)₂ Host

Abstract

Adjusting the local coordination environment of lanthanide luminescent ions is a useful method to manipulate the relevant photoluminescence (PL) property. K3Lu­(PO4)2 is a phase-change material, and according to the stable temperature range from low to high, the related polymorphs are phase I [P21/m, coordination number (CN) of Lu3+ = 7], phase II (P21/m, CN = 6), and phase III (P3̅, CN = 6), respectively. Based on the temperature-dependent PL analysis of K3Lu­(PO4)2:Pr3+, we find that Pr3+ ions occupy the noninversion sites (C s ) in the two low-temperature phases but preferentially enter into the inversion ones (C 3i ) in phase III. Compared to Pr3+-doped phase I (78 K), Pr3+ ions in phase III (300 K) manifest a weaker fluorescence intensity (170-fold lower). To enhance the room-temperature PL property of K3Lu­(PO4)2:Pr3+, a polymorphous adjustment strategy was proposed by the use of the ion-doping method. By introducing the Gd3+ ions into the lattice, Pr3+-doped phase I is successfully stabilized to room temperature, manifesting a 27-fold fluorescence increase in comparison to K3Lu­(PO4)2:Pr3+ (0.1 at. %). The finding discussed in this study highlights the significance of site engineering for luminescent ions and also presents the application value of phase-change hosts in the development of high-performance luminescent materials.

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

“…In addition, the Pr 3+ -doped concentration of 5 at % made the crystal structure of Pr 3+ :K 3 Lu­(PO 4 ) 2 maintain phase II at RT . Furthermore, the substitution of Gd 3+ ions for Lu 3+ ones in Pr 3+ :K 3 Lu 0.999– x Gd x (PO 4 ) 2 successfully stabilized low-temperature phases (phase I or phase II) to RT by changing the Gd 3+ -doped content . Accordingly, the larger rare-earth trivalent ions can modulate the stable temperature ranges of phases I and II of K 3 Lu­(PO 4 ) 2 .…”

“…37 Furthermore, the substitution of Gd 3+ ions for Lu 3+ ones in Pr 3+ :K 3 Lu 0.999−x Gd x (PO 4 ) 2 successfully stabilized low-temperature phases (phase I or phase II) to RT by changing the Gd 3+ -doped content. 38 Accordingly, the larger rare-earth trivalent ions can modulate the stable temperature ranges of phases I and II of K 3 Lu(PO 4 ) 2 . On this basis, the variation of Eu 3+ -doped content is also feasible for stabilizing the low-temperature phases to RT due to the larger ion radius of Eu 3+ ions in reference to that of Lu 3+ ones.…”

“…K 3 RE­(PO 4 ) 2 (RE = Y, Sc, and lanthanides) is one kind of promising phase-transition phosphate host whose crystal structure can be modified by temperature and RE 3+ ions. , The lanthanide-doped K 3 RE­(PO 4 ) 2 hosts showed great potential in various fields, including emission tunability, optical temperature sensing, and scintillation. − K 3 Lu­(PO 4 ) 2 , as a member of K 3 RE­(PO 4 ) 2 , possesses three kinds of temperature-dependent phases, corresponding to two low-temperature monoclinic phases (phases I and II) and one room-temperature hexagonal phase (phase III). Some reports have indicated that Ce 3+ - and Pr 3+ -doped K 3 Lu­(PO 4 ) 2 are outstanding scintillator materials due to their superior fast and efficient scintillation properties accompanied by the related phase transformations. − Additionally, our team investigated the influence of the polymorphic K 3 Lu­(PO 4 ) 2 structure on the PL properties of Pr 3+ ions in the region of 4 f → 4 f transitions in detail and successfully realized the related fluorescence enhancement by considering the properties of polymorphous influence …”

“…35−37 Additionally, our team investigated the influence of the polymorphic K 3 Lu(PO 4 ) 2 structure on the PL properties of Pr 3+ ions in the region of 4f → 4f transitions in detail and successfully realized the related fluorescence enhancement by considering the properties of polymorphous influence. 38 Thus, we brought the Eu 3+ ions into the phase-change K 3 Lu(PO 4 ) 2 host in this study and systematically investigated the polymorphism effect on the fluorescence performance of Eu 3+ ions. Our results revealed that the crystal-field splittings of Eu 3+ ions are different in the different phases due to the change in the local coordination environment.…”

Investigation of Rare Earth-Containing Double Phosphates of the Type A3Ln(PO4)2 (Ln = Y, La, Pr, Nd, and Sm–Lu) as Potential Nuclear Waste Forms

“…The alkali rare earth double phosphates with a stoichiometry of A 3 Ln­(PO 4 ) 2 have recently attracted attention for a variety of applications, including use as potential laser materials and γ-ray scintillators. − A series of potassium rare earth double phosphates [K 3 Ln­(PO 4 ) 2 (Ln = Sc, Y, La–Nd, and Sm–Lu)] was recently synthesized as single crystals from a potassium pyrophosphate (K 4 P 2 O 7 ) flux, and their structures were determined by single-crystal X-ray diffraction . Several properties of the K 3 Ln­(PO 4 ) 2 analogues have been measured, including formation enthalpies, reversible phase transitions between the low-temperature monoclinic and high-temperature trigonal structures, , and optical spectroscopy to obtain excitation and luminescence spectra of Ce-, Pr-, Eu-, and Tb-containing analogues. − In the context of nuclear materials, these structural transitions are of concern due to potential changes in the density, and thus molar volume, and crystallinity of potential TRU-containing materials. To date, little is known about the rubidium-based rare earth double phosphates, Rb 3 Ln­(PO 4 ) 2 , with their characterization limited to the structural determination and formation enthalpy determination of Rb 3 Lu­(PO 4 ) 2 and solely the structural determination of Rb 3 Er­(PO 4 ) 2 …”