Molten chloride synthesis, structural characterisation and luminescence spectroscopy of ultrafine Eu3+-doped BaTiO3 and SrTiO3

We report on the synthesis in molten NaCl, the morphological and structural characterisation and the luminescence spectroscopy of ultrafine BaTiO3 and SrTiO3 doped with Eu3+. The synthesis yields monophasic tetragonal BaTiO3:Eu3+ and cubic SrTiO3:Eu3+. Crystals of SrTiO3 have a cubic habit and size of about 200 nm, whereas BaTiO3 is composed of micrometer-sized interpenetrated crystals with more rounded shapes. A large amount of lattice disorder is present inside the crystals, especially in the BaTiO3 sample. The luminescence spectrum of ultrafine SrTiO3:Eu3+ is dominated by the D-5(0) --> F-7(2) transition, suggesting a strong distortion of the Eu3+ sites. The disorder contributes, together with the presence of numerous charge compensation mechanisms, to the strong inhomogeneous broadening of the D-5(0) --> F-7(J) luminescence bands of Eu3+. Ultrafine BaTiO3:Eu3+ is nonluminescent, presumably due to the higher concentration of defects, compared to the SrTiO3 host. (C) 2002 Elsevier Science B.V. All rights reserved.