Eu3+-site occupation in CaTiO3 perovskite material at low temperature

In order to clarify the site occupancy of rare-earth ions in rare-earth doped perovskite materials, the undoped pure CaTiO3 and Eu3+-doped CaTiO3 samples with a series of Ca/Ti ratio were synthesized via high-temperature solid-state reaction method. X-ray diffraction (XRD) powder patterns confirm that the crystal structure keeps invariant at various Ca/Ti ratios. Measurement results of unit-cell parameters and X-ray photoelectron spectroscopy (XPS) indicate that Eu3+ ions enter into the Ca2+ site. The highresolution photoluminescence spectra of Eu3+ ions at 20 K in all samples did not witness a significant change under the excitation at different wavelength, implying that Eu3+ ions occupy only one type of site. Considering the small spectral splitting range of D-5(0) -> F-7(2) transition and the large intensity ratio of D-5(0) -> F-7(2)/D-5(0) -> F-7(1), it can be concluded that Eu3+ occupies Ca2+ site with larger coordinate numbers rather than Ti4+ site. (C) 2016 Elsevier B. V. All rights reserved.