Green-Emitting Gd3Ga5O12: Tb3+ Nanoparticles Phosphor: Synthesis, Structure, and Luminescence

Nano- and microceramics of Gd3Ga5O12 garnet doped with 1 mol % Tb3+ ions were synthesized via co-precipitation and high-temperature solid-state reaction methods. X-ray diffraction measurements confirmed the formation of the garnet structure with Ia3d space group in all investigated samples. Atomic force microscopy surface images and grain-size distribution diagrams of Gd3Ga5O12: 1 mol % Tb3+ nanoceramics with 300 and 400 g/mol of polyethylene glycol (PEG) were obtained. The relationship between the content of polyethylene glycol and the particle size of Gd3Ga5O12: Tb3+ phosphors was revealed. An intense broad band (λ m = 266 nm) related to spin-allowed 4f 8-4f 75d 1 transitions of Tb3+ ions was found in photoluminescence excitation spectra of Gd3Ga5O12: Tb3+ nanocrystalline ceramics with PEG-300 and PEG-400 at 300 K. The broad excitation band caused by spin-forbidden (λ m = 295 nm) 4f-5d transitions in Tb3+ ions was additionally observed in the photoluminescence excitation spectra of Gd3Ga5O12: Tb3+ microceramics. Emission of Tb3+ ions under X-ray and UV excitations is presented by two groups of sharp lines which correspond to 5D3 and 5D4 → 7Fj transitions of Tb3+ ions with the most intense line at 546 nm (5D4 → 7F5). It was established that the increasing of PEG content leads to the decreasing of the X-ray and photoluminescence emission intensities.