Terbium photoluminescence in yttrium aluminum garnet xerogels

Based on a colloidal solution containing terbium, yttrium, and aluminum metal ions, a powder was synthesized and films of terbium-doped yttrium aluminum garnet Tb_0.15Y_2.85Al₅O₁₂ were grown on single-crystal silicon and porous anodic alumina. Annealing of the sample in a temperature range from 200–1100°C results in an increase in the photoluminescence intensity in the wavelength range from 480–640 nm, which is caused by Tb³⁺ ion intra-atomic transitions ⁵ D ₄→⁷ F _j (j = 3, 4, 5, 6). Annealing at 900°C and higher temperatures gives rise to low-intensity photoluminescence bands in the region of 667 and 681 nm, which correspond to transitions ⁵ D ₄→⁷ F ₀, ⁵ D ₄→⁷ F ₁, and room-temperature Stark term splitting, which suggests the existence of a crystalline environment of Tb³⁺ ions. The FWHM of spectral lines in the region of 543 nm decreases from ～10 to ～(2–3) nm as the xerogel annealing temperature is increased from 700 to 900°C and higher. Three bands with maxima at 280, 330, and 376 nm, which correspond to Tb³⁺ ion transitions ⁷ F ₆→⁵ I ₈, ⁵ L ₆, ⁵ G ₆, ⁵ D ₃, are observed in the photoluminescence excitation spectra of the studied structures for the emission wavelength at 543 nm. X-ray diffraction detected the formation of a crystalline phase for a terbium-doped yttrium aluminum garnet powder after annealing at 1100°C.