Effect of Yb doping concentration on crystallization kinetics in yttrium aluminum garnet nano-powders

Different ytterbium concentration-doped yttrium aluminum garnet (Yb:YAG) nanopowders were synthesized using coprecipitation with nitrate salts as the starting materials. The phase evolutions, morphologies, and microstructures of the powders synthesized from various ytterbium-doped precursors were investigated. Ytterbium doping concentration was discovered to have a crucial effect during the YAG phase formation from the precursor. Crystallized Yb:YAG powders were directly obtained at temperatures as low as 900 °C without the formation of any intermediate phase. The crystallization kinetics of the Yb:YAG precursors were analyzed using non-isothermal differential scanning calorimetry. Avarami parameters of 0.97, 1.00, 1.13, and 1.21 were obtained for Yb doping concentrations of 0, 3, 6, and 9 at% respectively, and crystallization activation energies of 1506±40, 1342±36, 1171±31, and 978.1±26 kJ/mol were calculated. The activation energy for YAG crystallization was lower when a high Yb doping concentration was used because the presence of Yb3+ prohibited the presence of anionic SO42− in the precursors, thus enhancing the elemental diffusion between particles. Both the average grain size and particle size of Yb: YAG decreased when Yb doping concentration was increased, and at various calcination temperatures.