Structural and Optical Investigations of Ce 3+ /Mn 2+ -Doped LaPO 4 Phosphors

Lanthanum orthophosphate (LaPO 4 ) and La 0.95− x Ce 0.05 Mn x PO 4 ( x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO 4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO 4 crystalline structure and an increase of the lattice strain as a consequence of the Mn 2+ and Ce 3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 ± 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn 2+ in isolated species, but also as agglomerates. Ce 3+ and Mn 2+ doping of LaPO 4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce 3+ to Mn 2+ ions, green emission of Mn 2+ ions at around 550 nm was observed upon 275 nm excitation.