Green-Emitting GdGaO: Tb Nanoparticles Phosphor: Synthesis, Structure, and Luminescence.

Nano- and microceramics of GdGaO garnet doped with 1 mol % Tb 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 GdGaO: 1 mol % Tb 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 GdGaO: Tb phosphors was revealed. An intense broad band (λ  = 266 nm) related to spin-allowed 4f -4f 5d transitions of Tb ions was found in photoluminescence excitation spectra of GdGaO: Tb nanocrystalline ceramics with PEG-300 and PEG-400 at 300 K. The broad excitation band caused by spin-forbidden (λ  = 295 nm) 4f-5d transitions in Tb ions was additionally observed in the photoluminescence excitation spectra of GdGaO: Tb microceramics. Emission of Tb ions under X-ray and UV excitations is presented by two groups of sharp lines which correspond to D and D → F transitions of Tb ions with the most intense line at 546 nm (D → F). It was established that the increasing of PEG content leads to the decreasing of the X-ray and photoluminescence emission intensities.