SYNTHESIS OF NANOSTRUCTURED CERIUM-DOPED YTTRIUM-ALUMINUM GARNETS BY METHOD OF SOL-GEL BURNING IN A MICROWAVE OVEN

The aim of research is to study the new method of thermochemical synthesis of yttrium-aluminum garnet luminescent powder, cerium doped (Y3Al5O12:Се3+, YAG:Ce) using the nitric acid salts of yttrium, aluminum and cerium, with the mixture of carbamide and hexamethylenetetramine used as fuel. Synthesis was performed in a microwave oven with the power of 800 W and frequency of 2450 MHz in a porcelain crucible closed with a perforated heat-resistant cover. The average size of coherent scattering region (CSR) of YAG:Ce particles (nominal diameter D) obtained in the crucible during the microwave heating is 50.3 nm. It has been established that when YAG powder is produced by burning, the reaction cup reaches the temperature sufficient for Y3Al5O12 compound synthesis, and that the reducing environment arising due to the combustion of the organic mixture contributes to formation of Ce ions in tricharged state. Further calcination of the resulting powder at the temperature of 450, 900 and 1100 ºC in the open air leads to formation of practically single-phase YAG structure. The radiation spectrum of the obtained YAG:Ce luminescent powders has a wide bandwidth caused by the energy transitions of Ce3+ ion in the garnet structure between 490 and 750 nm at LED excitation at 450 nm. It corresponds to yellow-green radiation that with blue LED radiation creates the sensation of white light. The highest intensity of the yellow-green luminescence is reached by the YAG:Ce powders calcinated at 900 ºC in the open air.