Luminescent and optical properties of complex oxyfluoride crystals

摘要

Spectra of photoluminescence (PL) and X-ray excited luminescence (XRL) in region of 1.5-5.5 eV, time- resolved pulse cathode-luminescence (PCL) spectra, the temperature depending of the XRL, luminescence decay kinetics were studied in crystals' family K_3WO_3F_3, Rb_2KTiOF_5, CsZnMoO_3F_3. All studied crystals are transparent from microwave to near UV range. PL, XRL spectra contain one broad band with the maximum in the region 2.0 - 2.7 eV, with great (～ 1.5 - 2.0 eV) Stokes shift. PL emission band is excited only in the region of long-wavelength fundamental absorption edge, selective bands in the region of crystal transparency are absent. PL decay kinetics contains components μs - range. PL yield increases in 15 - 20 times (with different activation energy) when cooled to T = 90 K. Emission of the main PL band in all crystals is connected to the intrinsic luminescence - the luminescence of self-trapped excitons. Emission is formed electronic transition in metal-(O, F) polyhedra. Despite different chemical composition luminescent crystal properties are based on similar physical properties and in many ways are identical to each other with the exception of the fact that emission band has different Stokes shift depending on the sample. This difference is due to the presence local distortion in the octahedron WO_3F_3, TiOF_5 and MoO_3F_3 in crystal lattice.