Abstract
Polymorphs of KNdW2O8 (α-KNdW2O8 and β-KNdW2O8)
phosphors were synthesized by an efficient solution combustion technique for
the first time. The crystal structure of the polymorphs analyzed from Rietveld
refinement of neutron diffraction data confirms that α-KNdW2O8 crystallizes in
the tetragonal system (space group I4̅), and β-KNdW2O8 crystallizes in the
monoclinic system (space group C2/m). The local structure of both polymorphs
was elucidated using combined neutron pair distribution function (PDF) and
Raman scattering techniques. Photoluminescence measurements of the
polymorphs showed broadened emission line width and increased intensity for
β-KNdW2O8 in the visible region compared to α-KNdW2O8. This phenomenon is
attributed to the increased distortion in the coordination environment of the
luminescing Nd3+ ion. Combined PDF, Rietveld, and Raman measurements reveal
distortions of the WO6 octahedra and NdO8 polyhedra in β-KNdW2O8. This
crystal structure−photoluminescence study suggests that this class of tungstates can be exploited for visible light emitting devices
by tuning the crystal symmetry.
