Luminescence and structural study of Bi 4− xEu xTi 3O 12 solid solution

Abstract

The Bi 4Ti 3O 12 (BIT) is a well known ferroelectric ceramic within the family of so called Aurivillius phases. The present work shows that when bismuth (Bi 3+, r = 0.96 Å) is substituted by trivalent europium ( r = 0.95 Å), a solid solution, Bi 4− x Eu x Ti 3O 12 (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 Bi 3+. We found at least two Eu 3+ sites, selectively excited. The Eu 3+ emission spectra reveal a significant rising of the point symmetry at the rare earth site with respect to the Bi C 1, deduced from the crystallographic analysis.