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

Abstract

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:Eu and GdPO₄:Eu³⁺ powders showed red emission bands originating from the ⁵DOₒ - ⁷Fᴊ (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.