NaBa_1−xCa_xPO₄:Eu²⁺ were synthesized using polymerizable complex method. New phases were observed at x = 1/3 and 0.5, which were identified by single-crystal XRD analysis as Na₃Ba₂Ca(PO₄)₃ and NaBa_0.5Ca_0.5PO₄ with a trigonal system. Though both phases pretend to be solid solutions between NaBaPO₄ and NaCaPO₄, they have different coordination environments and PO₄ orderings. 1 mol% Eu²⁺-activated NaBaPO₄, Na₃Ba₂Ca(PO₄)₃, and NaBa_0.5Ca_0.5PO₄ exhibited an emission maximum at 435 nm, 458 nm, and 460 nm, respectively. The shift of the emission maximum might be due to a change in the Eu–O bond length.