Preparation and photoluminescence of Eu²⁺ and Eu³⁺-doped NaLuO₂

Single phase NaLuO2, which crystallizes in the α-NaFeO2-type structure (trigonal, space group R3m), was synthesized by heating a mixture of Na2O and Lu2O3 at 1150 °C. The crystal structure of this oxide was analyzed using the Rietveld method for the powder X-ray diffraction pattern, and the oxygen atom coordinate [z = 0.2397(3)] was refined. Mixtures of NaLuO2 and europium monoxide with a composition NaLuO2–xEuO (x = 0.0, 0.01, 0.1, 1.0 mol %) were heated at 900 °C for 12 h in a N2 atmosphere. The obtained samples were Eu2+ and Eu3+-doped NaLuO2 with trace amounts of Lu2O3. The emission spectrum peak due to the 5d → 4f transition of Eu2+ occurred at a wavelength of 617 nm under the excitation of a 442 nm blue light, and the full width at half maximum of the spectrum was 80 nm. Intense emission peaks due to the f-f transition of Eu3+ were observed at approximately 590 nm when excited by a 230 nm ultraviolet light.