Structural, optical and EPR studies of NaCe(PO3)4 metaphosphate doped with Cr3+

Abstract The undoped and Cr 3+ -doped NaCe(PO 3 ) 4 metaphosphates were synthesized by the modified Pechini method and obtained as the crystalline powders. They were characterized by means of X-ray diffraction, vibrational and optical spectroscopy to clarify the structure and mechanism of Cr 3+ emission in NaCe(PO 3 ) 4 . This phosphor crystallizes in the monoclinic P12 1 /n1 structure with an infinite (PO 3 ) n chain. The Cr 3+ ions can substitute the C 1 symmetry site occupied by cerium ions. They can also occupy the tunnels formed in the anionic layer. Spectroscopic properties of the Cr 3+ and Ce 3+ ions were discussed in terms of structure of the studied crystalline powders. IR and Raman data confirm the predicted structure and indicate C 1 site symmetry of the Cr 3+ active ions. The Cr 3+ ions appear in the distorted octahedral environment of the weak crystal field. Optical studies were confirmed by EPR results carried out in the temperature range of 4–293 K. In addition, the magnetic measurements were performed up to 305 K. The Cr 3+ ions reveal negligible ferromagnetic interactions while the Ce 3+ ions change their magnetic interactions from slightly antiferromagnetic to significantly ferromagnetic above 20 K.