Fabrication and luminescence properties of Al2O3:Tb3+ microspheres via a microwave solvothermal route

► Al2O3:Tb3+ phosphors prepared via a microwave solvothermal route. ► The particles were hierarchically nanostructured microspheres packaged by nanosheets. ► 5D4→7F5 electric dipole transition is the most intensive when excited at 235 nm. ► 0.7 mol% of doping concentration of Tb3+ ions in γ-Al2O3:Tb3+ is optimum. ► Critical distance between Tb3+ ions for energy transfer is 18.4 Å.