Improved optical photoluminescence by charge compensation and luminescence tuning in Ca6Ba(PO4)4O:Ce3+, Eu2+ phosphors

Abstract

We comparatively investigated the effect of different charge compensators (Li⁺, Na⁺, K⁺ and Si⁴⁺) via the charge balance strategies of (i) 2Ca²⁺ → Ce³⁺ + M⁺ (M = Li, Na, K) and (ii) Ca²⁺ + P⁵⁺ → Ce³⁺ + Si⁴⁺ on the photoluminescence (PL) properties of blue-emitting Ca₆Ba(PO₄)₄O:Ce³⁺ phosphors. The optimized emission intensity was realized in Ca₆Ba(PO₄)₄O:Ce³⁺ with codoping Li⁺. The different charge compensation mechanisms and PL enhancement were analysed. Moreover, tunable luminescence can be further achieved through the introduction of Eu²⁺ into the Ca₆Ba(PO₄)₄O:Ce³⁺, Li⁺ phosphor, and charge compensation also plays an important role in the optimization of luminescence behaviours. It is proved that the emission spectra of Ca₆Ba(PO₄)₄O:Ce³⁺, Li⁺, Eu²⁺ can be tuned from 463 to 528 nm through Ce³⁺–Eu²⁺ energy transfer (ET). The intrinsic ET mechanism and process have also been studied.