The chemical unit was engineered by substituting Ga ³⁺ for Al ³⁺ in CaAl ₁₂ O ₁₉ :Mn ⁴⁺ .

A series of Eu²⁺ and Mn²⁺ activated novel Sr₃GdNa(PO₄)₃F phosphors have been prepared through a high temperature solid state reaction. The investigation revealed that Sr₃GdNa(PO₄)₃F crystallized in a hexagonal crystal system with the space group P (no. 147). The Eu²⁺ activated phosphors can be efficiently excited in the range of 250 to 420 nm, which matches well with the commercial n-UV LED chips, and give intense blue emission centering at 470 nm. By codoping the Eu²⁺ and Mn²⁺ ions into the SGNPF host and singly varying the doping content of the Mn²⁺ ion, tunable colors from blue to white and then to yellow are obtained in SGNPF:Eu²⁺,Mn²⁺ phosphors under the irradiation of 390 nm. The energy transfer from the Eu²⁺ to Mn²⁺ ions is demonstrated to be a dipole–quadrupole mechanism in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors. The critical distance between the Eu²⁺ and Mn²⁺ ions in SGNPF:Eu²⁺,Mn²⁺ was determined by the spectral overlap method. The investigation indicates that our prepared samples might have potential application in WLEDs.