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

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 0.01 Tb 0.1 BO 3 (RE = Lu 0.5 Gd 0.39 , Lu 0.5 Y 0.39 , and Y 0.5 Gd 0.39 ). The X-ray diffraction spectrum of yttrium orthoborate Y 1 – x – y Ce x Tb y BO 3 is described by a hexagonal lattice with space group P 6 3 / m , which, after annealing at 970°C, transforms into a monoclinic lattice with space group C 2/ c . High-temperature annealing of the studied orthoborates leads to a multiple, more than two orders of magnitude, increase in the luminescence intensity of Tb 3+ 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 Ce 3+ ions in the orthoborates at high temperatures. It is shown that the luminescence of terbium ions is due to energy transfer from Ce 3+ to Tb 3+ , which proceeds with high efficiency (∼85%) by the mechanism of dipole-dipole interaction between cerium and terbium.