Ionic conductivity and luminescence of Eu3+-doped LiTi2(PO4)3

Li1.3Eu0.3Ti1.7(PO4)3 and Li1.3Al0.3Ti1.7(PO4)3 doped with Eu3+ and Al3+ ions have been prepared by solid state reaction. It was found that the dopant Eu3+ ions enhanced the ionic conductivity of LiTi2(PO4)3 with the same increment as that of Al3+ ions at different temperatures. The mechanism has been investigated by XRD and luminescence probe. The result of XRD for Li1.3Eu0.3Ti1.7(PO4)3 indicates that the XRD patterns do not change with the doping of Eu3+. Luminescence spectra under various temperatures show that Eu3+ ions locate at the sites with inversion symmetry. The above results agree with the assumption that a glassy phase Li3Eu2(PO4)3 might be formed in the grain boundary of LiTi2(PO4)3, which increases the interface conduction layer and the contact area between grains and therefore may be responsible for the enhanced ionic conductivity.