Site-Selective Doping and Site-Sensitive Photoluminescence of Eu3+ and Tb3+ in Perovskite-Type LaLuO3

Abstract

Eu³⁺ and Tb³⁺ ions were site-selectively doped into LaLuO₃ with the orthorhombic perovskite-type structure (ABO₃), and their luminescence properties were examined considering the doping sites (A or B sites). The X-ray diffraction analysis revealed the expansion or contraction of the unit cell volumes of the materials depending on the doping sites. The spectra of X-ray absorption near edge structure for the Eu and Tb L_III edge exhibited different shapes for the ions at A and B sites, confirming the site-selective doping of Eu³⁺ and Tb³⁺ in LaLuO₃. The photoluminescence (PL) and PL excitation (PLE) spectra of the materials also showed some differences caused by the doping sites. The intensities of the Eu³⁺ PL peaks derived from the ⁵D₀–⁷F₁ transitions and those from the ⁵D₀–⁷F₂ transitions were markedly different between Eu³⁺ at A sites and those at B sites because of the different site symmetries. The splitting of the intense Tb³⁺ PL peaks originating from the ⁵D₄–⁷F₅ transitions and the absence of PL peaks from ⁵D₃–⁷F_J transitions were found only for Tb³⁺ at B sites because of the strong crystal field at B sites. In addition to the PL spectra, the positions of PLE peaks originating from charge transfer transitions in Eu³⁺ and the 4f–5d transitions in Tb³⁺ depended on the doping sites. The successful site-selective doping enabled us to clarify the site-sensitive luminescence properties of Eu³⁺ and Tb³⁺ doped in the perovskite-type LaLuO₃.