Abnormal blue-shift of Eu2+-activated calcium zirconium phosphates CaZr4(PO4)6

The electronic structure of CaZr4(PO4)(6) was calculated using the CASTEP code and the band gap for CaZr4(PO4)(6) can reach up to 4.30 eV. Ca1-xEuxZr4(PO4)(6) (0.01 <= x <= 1) samples were prepared by a high temperature solid-state reaction method. XRD analysis shows that Eu2+ ion can be totally incorporated into CaZr4(PO4)(6) forming complete solid solutions with trigonal lattice. Ca1-xEuxZr4(PO4)(6) (0.01 <= x <= 1) shows typical broad band emission in wavelength range from 400 to 650 nm for both under ultraviolet (UV) light and X-ray excitation, originating from the 4f(6)5d(1) -> 4f(7)5d(0) transition of Eu2+ ions. With increasing Eu2+ concentration, there is abnormal blue-shift of the emission peaks for Ca1-xEuxZr4(PO4)(6) due to the decreasing crystal field strength and Stokes shift. With increasing temperature in CaZr4(PO4)(6): Eu2+, its emission bands show the anomalous blue-shift with decreasing intensity. The overall scintillation efficiency of Ca0.9Eu0.1Zr4(PO4)(6) is 1.7 times of that of Bi4Ge3O12 (BGO) powder under the same conditions. In addition, its predominant decay time is about 50 ns at room temperature. The potential application of Eu2+-doped CaZr4(PO4)(6) has been pointed out. (C) 2015 Elsevier B.V. All rights reserved.