Fabrication of oriented oxide films from exfoliated yttrium hydroxide layers: Enhanced photoluminescence and unexplored behavior of energy transfer

Highlights: • Highly [111] oriented Y₂O₃ film was achieved by annealing of LRH film. • The enhanced photoluminescence of film was due to the higher exposure of (222) facets. • Color-tunable films were obtained through adjusting the incorporated activation ions. • Energy transfer from Tb³⁺ to Eu³⁺ was observed for the alternatively multilayer film. Layered yttrium hydroxide (LYH) nanospalates doped with different activators (Tb³⁺ and/or Eu³⁺) were hydrothermally synthesized and then successfully delaminated into ultrathin nanosheets of down to 1–3 nm thickness via intercalation reactions and mechanical agitation. Using the LYH nanosheets, highly [001] oriented yttrium hydroxide films were constructed through spin-coating. Based on the quasi-topotactic transformation from yttrium hydroxide to cubic Y₂O₃, [111] oriented oxide films were achieved by proper annealing. For the highly oriented Y₂O₃:0.05Eu film, the enhanced photoluminescence was obtained compared with the powder form due to the higher exposure of (222) facets. Through adjusting the incorporated activation ions, films with different color were obtained, and energy transfer from Tb³⁺ to Eu³⁺ was observed for the alternatively multilayer film, although Eu³⁺ and Tb³⁺ were located in different layers.