摘要
The crystals of NaLn(WO4)_2(Ln=La,Pr,Nd)are grown from a melt of LiCl-Na_2WO_4 flux by slow cooling method.The chemical analysis data show that the crystals are NaLa(WO_4)_2,NaPr(WO4)_2 and NaNd(WO_4)_2 respectively.The structures of the crystals are ascertained that they belong to scheelite structure of the tetragonal system with a space group of 14_1/a.The lattice parameters of the crystals have been calculated.It is found that the cell volume of NaLn(WO_4)_2 crystals decrease with a decrease of Ln^(3+)radius. The bond distances and their angles in NaLa(WO_4)_2 and NaNd(WO_4)_2 are given.It is found that in accordance with the decrease of ionic radii of Ln^(3+)due to increase of atomic number,the bond distances between Ln-O,Ln-Ln and W-O decrease regularly.The infrared spectra of NaLn(WO_4)_2 are measured.The tetrahedra characteristic absorptions of WO_4^(2-)are shown.The sensitization of host lattice is observed from the excitation and fluorescent spectra of NaLa(WO_4)_2 and NaPr(WO_4)_2.
The crystals of NaLn(WO4)_2(Ln=La,Pr,Nd)are grown from a melt of LiCl-Na_2WO_4 flux by slow cooling method.The chemical analysis data show that the crystals are NaLa(WO_4)_2,NaPr(WO4)_2 and NaNd(WO_4)_2 respectively.The structures of the crystals are ascertained that they belong to scheelite structure of the tetragonal system with a space group of 14_1/a.The lattice parameters of the crystals have been calculated.It is found that the cell volume of NaLn(WO_4)_2 crystals decrease with a decrease of Ln^(3+)radius. The bond distances and their angles in NaLa(WO_4)_2 and NaNd(WO_4)_2 are given.It is found that in accordance with the decrease of ionic radii of Ln^(3+)due to increase of atomic number,the bond distances between Ln-O,Ln-Ln and W-O decrease regularly.The infrared spectra of NaLn(WO_4)_2 are measured.The tetrahedra characteristic absorptions of WO_4^(2-)are shown.The sensitization of host lattice is observed from the excitation and fluorescent spectra of NaLa(WO_4)_2 and NaPr(WO_4)_2.
