Luminescence and structural study of Bi4−xEuxTi3O12 solid solution

The Bi4Ti3O12 (BIT) is a well known ferroelectric ceramic within the family of so called Aurivillius phases. The present work shows that when bismuth (Bi3+, r = 0.96 Å) is substituted by trivalent europium (r = 0.95 Å), a solid solution, Bi4−xEuxTi3O12 (BIET), is formed. This solid solution was obtained by coprecipitation and characterized by X-ray diffraction, electron microscopy and density measurements. The solubility limit x was determined, and the variation of the lattice parameters was measured through profile fitting of the whole pattern. In order to establish the europium substitution site, we studied the luminescent properties of the material. The excitation spectra, at room temperature, show a broad band associated with a charge transfer state and with the intrinsic absorption of Bi3+. We found at least two Eu3+ sites, selectively excited. The Eu3+ emission spectra reveal a significant rising of the point symmetry at the rare earth site with respect to the Bi C1, deduced from the crystallographic analysis.