Cation-tunable blue phosphor Ca₂PO₄Cl:Eu²⁺: enhancive emission and site occupancy

A series of blue phosphors Ca(1.98-x)M(x)PO4Cl:0.02Eu(2+) (M = Mg and Sr) with different values of x were synthesized using a high-temperature solid-state reaction. X-Ray diffraction and photoluminescence measurements were used to study the phase structure and luminescence properties. Ca2PO4Cl:0.02Eu(2+) exhibits a tunable emission intensity and color due to the incorporation of Sr(2+) or Mg(2+). The incorporation of Sr(2+) reduces the luminescence intensity and results in a slight red shift in the emission band. The incorporation of Mg(2+) results in enhanced emission and a clear blue shift in the emission band along with a tunable chromatic coordination. Under excitation at λ = 334 nm, the emission intensity of the Mg(2+)-doped Ca2PO4Cl:0.02Eu(2+) is found to be 250% that of Ca2PO4Cl:0.02Eu(2+). The luminescence behaviors of the as-synthesized phosphors are discussed according to the host crystal structure and site occupancy of Eu(2+). The results indicate that Mg(2+)-doped Ca2PO4Cl:Eu(2+) is more applicable as a near-UV-convertible blue phosphor for white light-emitting diodes.