Flux Synthesis, Monoclinic Structure, and Luminescence of Europium(III)‐Doped K 3 La(PO 4 ) 2

Single crystals of potassium lanthanum orthophosphate are prepared from high‐temperature melts containing potassium molybdate as a flux and structurally investigated by single‐crystal X‐ray diffraction. The framework is shown to be constructed from isolated LaO 7 monocapped prisms and PO 4 tetrahedra through corner‐ and edge‐sharing giving rise to 2D sheets with composition [La(PO 4 ) 2 ] 3− . Three types of potassium cations reside between these layers. For the solid solutions K 3 La 1− x Eu x (PO 4 ) 2 ( x  = 0.1–0.9) prepared by the solid‐state route, the excitation and emission luminescence spectra are studied at room temperature. The emission spectra exhibit strong reddish performance, which is due to the 5 D 0 → 7 F J transitions of Eu 3+ ions. The correlation between the structure and the photoluminescent properties of the phosphors is studied. The energy transfer and concentration quenching of the phosphors are discussed. Solid solutions K 3 La 1− x Eu x (PO 4 ) 2 have a potential application for white‐light‐emitting diodes.