Nanothick aluminate long-afterglow phosphors using inherited hydrothermal deriving

Abstract

A novel strategy of the inherited hydrothermal method was used to prepare SrAl2O4: 0.01Eu2+, 0.01Dy3+ (SAO) without boron (ISAO) and boron-doping (BSAO) via NaAlO2 as an aluminum source and mineralizer at 200 °C for 6–24 h. The investigated optical properties was correlated to phase transformation and phosphor morphology. The main constituting phases of Al2(OOH)2 and SrCO3 transformed to monoclinic SrAl4O7 and mixed monoclinic/hexagonal SrAl2O4 then pure monoclinic SrAl2O4 during different hydrothermal period. The hydrothermally prepared samples exhibited flower-like morphology. The annealed plate phosphors with nanothick single crystals inherited from hydrothermal feature. The shift of photoluminescence (PL) peak wavelength corresponded to the phase transformation from SrAl4O7 to SrAl2O4 with hydrothermal time for ISAO and BSAO. The PL intensity increased with hydrothermal time due to achieving the pure SrAl2O4 phase with preferred orientation geometry and further enhanced by boron-doping. The afterglow of BSAO was significantly enhanced than ISAO, solid-state prepared MSAO and commercial SAO at the initial 100 s after excitation cut-off. The boron doped in the BSAO was scarcely on the grain surface as to small grain size. Thus, the afterglow enhancement should be attributed to the boron in the lattice inducing defect traps. Overall, the inherited hydrothermal and boron-doping derived nanothick SAOs with large surface preferred orientation enhanced the PL and afterglow properties.