Intrinsic and impurity luminescence of rare earth ions doped KYF4 nanophosphors

The KYF₄ nanopowders, non-doped and doped with Ce³⁺ or Tb³⁺, having well-crystallized, unaggregated, monodisperse (±15%) nanoparticles with the cubic (the size in the range from ∼15 to ∼30 nm) or hexagonal (from ∼30 to ∼50 nm) crystal structure have been successfully synthesized by microwave-hydrothermal treatment of as-precipitated gels. In KYF₄ hexagonal nanopowders an intense STE-type luminescence at ∼4.4 eV was observed which is not quenched at room temperature. In contrast to single crystals or cubic nanopowders, in KYF₄ hexagonal nanopowders doped with Ce³⁺ or Tb³⁺, a rather efficient energy transfer is observed from the host to Ce³⁺ or Tb³⁺ ions, respectively, because of overlapping the emission spectrum of STE-type luminescence and the spectrum of efficient absorption on 4f-5d transitions in Ce³⁺ or Tb³⁺.