Studies on terbium doped apatite phosphors prepared by precipitation under microwave conditions

Abstract In this study we present our first attempts to obtain silicate apatite phosphors by precipitation with NaOH under microwave conditions. Y and La precursors fired at different temperatures (800 °C÷1400 °C) led to phosphors with hexagonal apatite structure belonging to the space group P 63/m and with crystallites size up to 105 nm. The structure and chemical composition of samples were evaluated based on FTIR, XRD and ICP-OES while the morphology, surface state and porosity were revealed using SEM and BET investigations. The impact of the firing temperature on the purity phase, crystalline order degree, crystallites size and luminescent properties of the apatite phosphors are discussed. It was found that the nature of rare earth (Y 3+ or La 3+ ) same as the incorporation degree of activator (Tb 3+ ) is responsible for the apatites green - turquoise emission. ICP-OES measurements show that the Tb 3+ amount incorporated in the apatite lattice increase with firing temperature and is lower in La-phosphors compared with Y-phosphors. The 5 D 4 – 7 F 5 transition observed in the green spectral domain was dominant in Y- phosphors while 5 D 3 - 7 F 6,5,4 transitions from blue spectral region was dominant in La-phosphors. The chromatic coordinates shifts from green to turquoise with firing temperature and depends on the excitation radiation, indicating the applicative potential of these phosphors in display screens for solid-state lighting applications.