Molten salt synthesis, visible and near-IR region spectral properties of europium or neodymium doped CoNb2O6 columbite niobate

Pure Nd 3+ - or Eu 3+ -doped CoNb 2 O 6 powders have been prepared by a molten salt synthesis method using a Li 2 SO 4 -Na 2 SO 4 or NaCl-KCl salt mixture as a flux at relatively low temperatures as compared to the solid state reaction method. X-ray diffraction patterns of pure CoNb 2 O 6 samples indicated an orthorhombic single phase. For Eu 3+ -doped CoNb 2 O 6 samples, the luminescence of Eu 3+ was observed at 615 nm as red emission while the Nd 3+ doped sample showed a typical emission at 1064 nm varying with the Eu 3+ or Nd 3+ doping concentrations. These luminescence characteristics of the doped samples may be attributed to the energy transfer between rare earth ions and CoO 6 octahedral groups in the columbite structure. Emission spectra of the phosphor powders for the 5 D 0 → 7 F 2 transition in CoNb 2 O 6 powders doped with Eu 3+ at 300 K.