Facile hydrothermal synthesis and multicolor-tunable luminescence of YPO4:Ln3+ (Ln = Eu, Tb)

Abstract

Well-crystallized tetragonal YPO₄ and YPO₄:Ln³⁺ (Ln = Eu, Tb) nanocrystals with cuboid morphology and narrow size distribution have been successfully synthesized through a facile two-step hydrothermal synthesis route using Y₄O(OH)₉NO₃ as a sacrificial precursor for the first time. The structure, morphology and phase evolution process were significantly affected by the reaction conditions (hydrothermal treatment time and concentration of (NH₄)₂HPO₄). The luminescence colors of YPO₄:Tb³⁺, Eu³⁺ phosphors can be easily tuned from green to primrose yellow and then to white by adjusting the concentration of Eu³⁺ ions under 373 nm irradiation. Furthermore, the energy transfer efficiency of YPO₄:0.08Tb³⁺, xEu³⁺ increased gradually and reached about 94.30% when the concentration of Eu³⁺ ions was 0.10. The energy transfer mechanism from Tb³⁺ to Eu³⁺ has been proved to be a quadrupole–quadrupole interaction mechanism. These merits manifest that the yttrium phosphate phosphors with tunable white light emission may have potential applications in white light-emitting diodes.