Eu³⁺ spectroscopy: A structural probe for yttrium orthoborate phosphors

Yttrium orthorborate YBO₃ containing 0.5 or 5 atom % of Eu ³⁺ has been prepared by the spray-pyrolysis method. Low-temperature, high-resolution emission spectroscopy has been used to probe the local site symmetries of Eu³⁺ ions accommodated on the Y3+ sites in YBO ₃:Eu³⁺ (0.5 atom %) and hence to determine the crystal structure of the title compound. The use of point group selection rules enabled a consistent spectral interpretation by envisaging distinct C_i and C₁ symmetry Eu³⁺ sites, in accordance with the neutron diffraction study of Lin et al. (Chem. Mater. 2004, 16, 2418). The assignment of features in the 10 K visible absorption spectrum of YBO₃:Eu ³⁺ (5 atom %) is also consistent with the two-site model, but it was found that the site occupation by Eu³⁺ differs from the expected ratio 2C₁:1C_i. The fitting of 31 crystal-field levels of the C₁ site has been made with some approximations by employing 7 parameters. In addition, the emission spectrum of YBO₃:Eu ³⁺ containing a trace amount of Y₃BO₆ has been compared with those of YBO₃:Eu³⁺ and Y₃BO ₆: Eu³⁺, which serves as a reference to elucidate the concern on the red/orange color ratio of YBO₃:Eu³⁺ emission. © 2010 American Chemical Society.