Influence of crystalline structure on the luminescence properties of terbium orthotantalates.

Abstract

Terbium orthotantalate powders were produced with M-fergusonitetype (I2/a) and M0-fergusonite type (P2/a) structures.The samples were studied byX-ray diffraction, Ramans cattering, and photo luminescence measure ments (emission and decaycurves).The results showed that crystalline materials were obtained with all the 18Raman-active modes predicted by group theory alculations. Also, it was observed through photo luminescence ecay curves that the Tb3þ ions occupies only one- symmetry site in both crystal lographi arrangements. Photo luminescence emission curves exhibited some variation inspectral shape, peak position, and relative intensity asa consequence of their different crystal linear rangements. The dominated emission of Tb3þ (5D4-7F5) is centered with a maximum intensity at 549.2nm(M-type) and 543.0nm(M0-type). Fluorescence life times for M-TbTaO4 and M0-TbTaO4 were determinedas 33.4 ms and 1.25ms, respectively. M0-type materials seems to be the most suitable for luminescent devicesand could be a potential green luminescent material dueto the strongest mission if compared with the M-fergusonite type.