STRUCTURAL AND OPTICAL INVESTIGATIONS OF SODIUM EUROPIUM CARBONATE NA3EU(CO3)(3)

The crystal structure and the luminescence properties of a new carbona te, Na3Eu(CO3)(3), are presented, Na3Eu(CO3)(3) is orthorhombic, acent ric, Ama2, Z = 4; a = 9.942(2) Angstrom, b = 11.024(3) Angstrom, c = 7 .147(2) Angstrom; R = 0.019, R-W = 0.051, 2374 unique reflections. The anionic subnetwork is built up from the stacking of ''standing on edg e'' and ''flat lying'' carbonate layers into which Na+ and Eu3+ ions a re inserted. The symmetry of the EuO9 polyhedra is C-s. The Eu3+ lumin escence technique confirms the presence of a unique low symmetry site for the rare earth atom. The electrostatic crystal field (cf) effects on the F-7 multiplet are evaluated on the basis of the phenomenologica l cf theory. The simulation using C-2v symmetry for the rare earth ato m gives good agreement between the calculated and experimental F-7(0-6 ) energy level schemes (r.m.s. standard deviation 8.9 cm(-1)). Out of 49 theoretical F-7(JM) Stark components, 39 observed components are de duced from the absorption and emission spectra. (C) 1997 Academic Pres s.