Controllable structural ordering via chemical substitution to the efficient and thermally stable luminescence in NASICON-type phosphor Series: Na1+xHf2−xScx(PO4)3:Eu.

[Display omitted] • A controllable structural ordering is achieved in Na 1+ x Hf 2− x Sc x (PO 4) 3 :Eu series. • The PLQY values for all scandium-involved analogues are all higher than 90%. • Structural ordering guarantees the most thermally stable luminescence in NHS 0.3 :Eu. Exploring NASICON-type materials emerges the fully ordered NaHf 2 (PO 4) 3 compound. Its cation/vacancy distribution forms an absolutely structural ordering three-dimensional arrangement. Further preparing a solid solution following Na 1+ x Hf 2− x Sc x (PO 4) 3 :Eu (NHS x :Eu; 0.0 ≤ x ≤ 1.6) confirms all compounds are isostructural. Densely atomic-connected framework guarantees the efficient blue emission, which yields > 90% photoluminescence quantum yield (PLQY) for all scandium-substituted analogues, yet the existence of heavy amount of luminescence killer (Eu3+) limits the performance of NaHf 2 (PO 4) 3 :Eu as a luminescent phosphor. Moreover, a controllable structural ordering/disordering is achieved by varying x value, which is confirmed by Raman and 31P MAS NMR spectra. The structural ordering/disordering is crucial in determining structural rigidity. Consequently, despite the voids in the framework filled with sodium ions as x increases has positive contribution to the structural robustness, cation/vacancy ordered form still builds the most rigid structure for NHS 0.3 , as established by the NHS 0.3 composition possessing the highest Debye temperature within the scandium-involved analogues, which are extracted experimentally by the low temperature specific heat measurements. As such, NHS 0.3 :Eu has the best thermal stability across the x range, which keeps 90% of integrated intensity up to 203 ℃ compared with room temperature value. This work provides insight into the structural specialty of NASICON structure. [ABSTRACT FROM AUTHOR]