Effect of calcination temperature on phase evolution and photoluminescent properties of GdPO 4 :Eu 3+ nanoparticle phosphors synthesized by combustion method

Eu 3+ ‐doped GdPO 4 nanoparticles were synthesized by a straightforward combustion method using urea as fuel and metal nitrates as precursors. Structures, morphologies and photoluminescent properties of the synthesized samples were studied by X‐ray diffraction, scanning electron microscopy and photoluminescent spectroscopy. There are two types of crystal structures formed during the annealing process: hexagonal GdPO 4 .H 2 O and monoclinic GdPO 4 . The former can be found at low annealing temperatures (300‐500°C) while the latter can be obtained at higher annealing temperatures (700‐900°C). The average diameters for nanoparticles are 20‐30 nm. Under the excitation at 273 nm, both GdPO 4 .H 2 O:Eu 3+ and GdPO 4 :Eu 3+ powders showed red emission bands originating from the 5 D 0 ‐ 7 F J (J = 1, 2, 3 and 4) transitions of Eu 3+ . Their PL intensity and crystal structures exhibit a similar behavior as a function of the annealing temperature.