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

Abstract The electronic structure of CaZr 4 (PO 4 ) 6 was calculated using the CASTEP code and the band gap for CaZr 4 (PO 4 ) 6 can reach up to 4.30 eV. Ca 1− x Eu x Zr 4 (PO 4 ) 6 (0.01 ⩽ x ⩽ 1) samples were prepared by a high temperature solid-state reaction method. XRD analysis shows that Eu 2+ ion can be totally incorporated into CaZr 4 (PO 4 ) 6 forming complete solid solutions with trigonal lattice. Ca 1− x Eu x Zr 4 (PO 4 ) 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 4 f 6 5 d 1 → 4 f 7 5 d 0 transition of Eu 2+ ions. With increasing Eu 2+ concentration, there is abnormal blue-shift of the emission peaks for Ca 1− x Eu x Zr 4 (PO 4 ) 6 due to the decreasing crystal field strength and Stokes shift. With increasing temperature in CaZr 4 (PO 4 ) 6 : Eu 2+ , its emission bands show the anomalous blue-shift with decreasing intensity. The overall scintillation efficiency of Ca 0.9 Eu 0.1 Zr 4 (PO 4 ) 6 is 1.7 times of that of Bi 4 Ge 3 O 12 (BGO) powder under the same conditions. In addition, its predominant decay time is about 50 ns at room temperature. The potential application of Eu 2+ -doped CaZr 4 (PO 4 ) 6 has been pointed out.