Eu3+ Spectroscopy: A Structural Probe for Yttrium Orthoborate Phosphors

Yttrium orthorborate YBO 3 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 Eu 3+ ions accommodated on the Y 3+ sites in YBO 3:Eu 3+ (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 C 1 symmetry Eu 3+ 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 YBO 3:Eu 3+ (5 atom %) is also consistent with the two-site model, but it was found that the site occupation by Eu 3+ differs from the expected ratio 2 C 1:1 C i . The fitting of 31 crystal-field levels of the C 1 site has been made with some approximations by employing 7 parameters. In addition, the emission spectrum of YBO 3:Eu 3+ containing a trace amount of Y 3 BO 6 has been compared with those of YBO 3:Eu 3+ and Y 3 BO 6:Eu 3+, which serves as a reference to elucidate the concern on the red/orange color ratio of YBO 3:Eu 3+ emission.