Size and morphology-controlled synthesis of vernier yttrium oxyfluoride towards enhanced photoluminescence and white light emission

In this study, a class of vernier yttrium oxyfluoride (Y5O4F7 denoted as V-YOF) with a variety of shapes and sizes was formed by adjusting the crystal growth environment; after calcination, the samples can maintain the morphology of the precursor; this may be attributed to the topotactic chemical transformation. A comparison of the fluorescence results shows that the hexagonally shaped microcrystal strips can effectively improve the light-emitting characteristics; further, to explore the growth mechanism of precursors, time-dependent experiments and three-dimensional growth simulations have been carried out. They suggest that the formation of hexagonal strips may be due to the unique way that the crystals grow from the interior space to the outer wall. Moreover, Tm3+/Dy3+-codoped V-YOF phosphors exhibit excellent white light emission (CIE: x = 0.338, y = 0.313 close to that of standard white light (0.33, 0.33)) due to energy transfer. These results confirm that the V-YOF phosphors may have potential applications in the field of luminescent materials.