Eu_0.56Ta₂O₇:  A New Nanosheet Phosphor with the High Intrananosheet Site Photoactivator Concentration

High photoactivator concentration nanosheets Eu_0.56Ta₂O₇ have been prepared by the soft chemical exfoliation reaction of the layered perovskite Li_2-xH_xEu_0.56Ta₂O₇ with a tetrabutylammonium hydroxide aqueous solution. In-plane X-ray diffraction and TEM and AFM observation results indicate that the Eu_0.56Ta₂O₇ nanosheet is crystalline and retains the layered perovskite structural feature of the bulk precursors. The most intense emission is observed from the ⁵D₀ → ⁷F₂ transition of Eu³⁺. The intensity of this emission by the host excitation exceeds 18 times that by the direct Eu³⁺ excitation.