Structural and Luminescence Behavior of Nanocrystalline Orthophosphate K Me Y(PO 4 ) 2 : Eu 3+ ( Me = Ca, Sr) Synthesized by Hydrothermal Method.

K Me Y(PO 4 ) 2 :5% Eu 3+ phosphates have been synthesized by a novel hydrothermal method. Spectroscopic, structural, and morphological properties of the obtained samples were investigated by X-ray, TEM, Raman, infrared, absorption, and luminescence studies. The microscopic analysis of the obtained samples showed that the mean diameter of synthesized crystals was about 15 nm. The KCaY(PO 4 ) 2 and KSrY(PO 4 ) 2 compounds were isostructural and they crystallized in a rhabdophane-type hexagonal structure with the unit-cell parameters a = b ≈ 6.90 Å, c ≈ 6.34 Å, and a = b ≈ 7.00 Å, c ≈ 6.42 Å for the Ca and Sr compound, respectively. Spectroscopic investigations showed intense 5 D 0 → 7 F 4 transitions connected with D 2 site symmetry of Eu 3+ ions. Furthermore, for the sample annealed at 500 °C, europium ions were located in two optical sites, on the surface of grains and in the bulk. Thermal treatment of powders at high temperature provided better grain crystallinity and only one position of dopant in the crystalline structure. The most intense emission was possessed by the KSrY(PO 4 ) 2 :5% Eu 3+ sample calcinated at 500 °C.