Effect of calcination temperature on phase evolution and photoluminescent properties of GdPO4:Eu3+ nanoparticle phosphors synthesized by combustion method

Eu3+ ‐doped GdPO4 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 GdPO4.H2O and monoclinic GdPO4. 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 GdPO4.H2O:Eu3+ and GdPO4:Eu3+ powders showed red emission bands originating from the 5D0 ‐ 7FJ (J = 1, 2, 3 and 4) transitions of Eu3+. Their PL intensity and crystal structures exhibit a similar behavior as a function of the annealing temperature.