Spectroscopic and structural properties of Na3RE(PO4)2:Yb orthophosphates synthesised by hydrothermal method (REÂ =Â Y, Gd)

Na3RE(PO4)2 orthophosphates, where RE = Y and Gd, doped with Yb3+ ions were synthesised by hydrothermal method and characterised by X-ray diffraction, microscopic, IR and Raman techniques. The emission, excitation spectra were recorded at room temperature and fluorescence decay time was determined. As-synthesised samples crystallise in a trigonal modification and during calcination at 500 °C they transform to a monoclinic or orthorhombic symmetry (for yttrium and gadolinium compounds, respectively). Finally, the samples calcined at 700 °C do not reveal the trigonal symmetry. The morphology of particles for all samples is similar and resembles rice grains. All the obtained for the studied orthophosphates data were compared to those previously reported for the same compounds synthesised by Pechini method.