Phase Control of Eu³⁺-Doped YPO₄ Nano-/Microcrystals

The crystal phase control is one of the most important issues in materials science, because different atomic arrangements and electronic structures of crystals will endow materials with enhanced or new functionalities. However, exploring a general rule to the phase control is extremely difficult, since the formation of new crystal phases is usually induced by many reaction parameters or methods. Here we describe a Eu³⁺ (5 atom %)-doped YPO₄ nano-/microcrystal system in which the phase can be rationally tuned in hexagonal or tetragonal. We confirm that manipulating the relative concentrations of phosphate groups and free RE³⁺ ions in using different approaches in the reaction solution can determine the formation of the final crystallographic phase of the Eu³⁺-doped YPO₄ nano-/microcrystals. Experimental observations show crystal structure offering powerful control over the morphologies and optical emission properties of the resulting nano-/microcrystals. We believe that the structural control scheme, demonstrated here in Eu³⁺-doped YPO₄ nano-/microcrystals, could be extended to other inorganic nano-/microcrystal systems for their desirable applications and their correlated fundamental research.