Discovery Of A New Phosphor Via Aliovalent Cation Substitution: Dft Predictions, Phase Transition And Luminescence Properties For Lighting And Anti-Counterfeiting Applications

Over the last two decades, suitable compositions have been investigated to make new phosphors because they are key materials for use in solid-state lighting and security applications. Aliovalent cations have different radii, electronegativity and valence states, and can thus be used to remarkably modify crystal structures. Here, we report a new Sr33Lu6(PO4)(28) phase produced from Sr-3(PO4)(2)via the method of aliovalent cation substitution. Density functional theory calculations were used to predict the possibility of the formation of a new phase when substituting three Sr2+ for two Lu3+ ions in the material. The new phase, Sr33Lu6(PO4)(28), was confirmed by X-ray diffraction, electron diffraction and photoluminescence spectroscopy. Different from the purple phosphor Sr-3(PO4)(2):Eu2+, Sr33Lu6(PO4)(28):Eu2+ exhibits broad green emission under near-UV excitation due to the multi-site occupancy of Eu2+. Combining near-UV chip, blue, red and Sr33Lu6(PO4)(28):Eu2+ green phosphors, a white light-emitting diode with a high colour rendering index (similar to 92) was made, with potential lighting applications. Additionally, a transparent security ink fabricated using the Sr33Lu6(PO4)(28):Eu2+ phosphor shows high concealment and recognition. This work is not confined to the report of a new Sr33Lu6(PO4)(28):Eu2+ phosphor and its corresponding applications; it is expected that aliovalent cation substitution will be useful as a general method for the discovery of new materials.