Cation vacancy repair towards a new yellow Ca7Sr3Na(PO4)7:Eu2+ phosphor

Abstract Cationic substitution is a prevalent strategy to tune the luminescence spectra of phosphors. In this work, we reported a series of Eu 2+ -activated whitlockite type Ca 7 Sr 3.5-0.5 x A x (PO 4 ) 7 (CSPA; A =Li, Na, K) ( x  = 0–1.00) phosphors. The substitution by Na + for both half occupied/vacant M(4) site was verified via Raman spectra, Reitveld refinement and HR-TEM, whereas a similar accommodation of K + into the Ca 2 Sr(PO 4 ) 2 (CSP) host cannot be realized due to the significant size mismatch. A continuous increase of Na + contents led to the progressively structural contraction, promoting the migration of Eu 2+ activator from looser M(4) to other sites, and regulating the luminescence behaviors. Consequently, the gradual red-shift of emission band terminated at a new yellow phosphor Ca 7 Sr 3 Na(PO 4 ) 7 :0.04Eu 2+ . The cation vacancy repair developed in this work can not only migrate the Eu 2+ activator among different cation sites, but also serves as a new strategy for tuning the luminescence properties of phosphor.