YBO3:Tb3+ phosphors with nest-like and apple-like morphology were synthesized via the microemulsion-mediated hydrothermal process at a reaction temperature as low as 180 degrees C. This process significantly reduced the reaction duration and temperatures as compared with the conventional processes. The YBO3:Tb3+ powders prepared via the microemulsion-mediated hydrothermal process had smaller particle sizes in comparison with the hydrothermal process. In the growth process, the nanoflakes assembled to spheres in revolved order. Each nanoflake protruded out of the spheres, followed by transforming into completed multilayers to form the nest-like particles. When the prepared phosphors were excited with the wavelength of 240 nm, the emission peaks in the range from 487 to 628 nm are related to the transitions from D-5(4) to F-7(J) (J = 3-6) levels of Tb3+ ions. As the reaction temperatures were increased, the lifetimes were increased due to decrease in the defect centers. The reduced defect centers and enhanced crystallinity of the prepared samples cause the luminescent intensity to increase.