Energy Transfer from Ce3+ to Tb3+ in Yttrium and Gadolinium Orthoborates Obtained by Hydrothermal Synthesis

Abstract

We studied the structure, IR absorption spectra, the spectral characteristics of photoluminescence and morphology of cerium- and terbium-doped orthoborates of gadolinium and yttrium obtained by hydrothermal synthesis at 200°C, as well as solid solutions of orthoborates on the basis of yttrium, gadolinium, and lutetium with composition RECe_0.01Tb_0.1BO₃ (RE = Lu_0.5Gd_0.39, Lu_0.5Y_0.39, and Y_0.5Gd_0.39). The X-ray diffraction spectrum of yttrium orthoborate Y_{1 – x – y}Ce_xTb_yBO₃ is described by a hexagonal lattice with space group P6₃/m, which, after annealing at 970°C, transforms into a monoclinic lattice with space group C2/c. High-temperature annealing of the studied orthoborates leads to a multiple, more than two orders of magnitude, increase in the luminescence intensity of Tb³⁺ ions when the samples are excited in the absorption band of cerium ions. This effect is the result of a significant increase in the concentration of Ce³⁺ ions in the orthoborates at high temperatures. It is shown that the luminescence of terbium ions is due to energy transfer from Ce³⁺ to Tb³⁺, which proceeds with high efficiency (∼85%) by the mechanism of dipole-dipole interaction between cerium and terbium.