A new disordered langbeinite-type compound, KTbTaPO, and Eu-doped multicolour light-emitting properties.

For the first time, a new langbeinite-type phosphate, namely potassium terbium tantalum tris(phosphate), KTbTa(PO), has been prepared successfully using a high-temperature flux method and has been structurally characterized by single-crystal X-ray diffraction. The results show that its structure can be described as a three-dimensional open framework of [TbTa(PO)] interconnected by K ions. The Tb and Ta cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV-Vis spectrum, the morphology and the Eu-activated photoluminescence spectroscopic properties were studied. A series of Eu-doped phosphors, i.e. KTbTa(PO):xEu (x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid-state reaction and the photoluminescence properties were studied. The results show that under near-UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu concentration from 0 to 0.1, because of the efficient Tb→Eu energy-transfer mechanism.