The role of Eu2+ concentration on the phase formation and spectroscopic properties of MZr4(PO4)(6) (M2+ = Ca2+, Sr2+)

Abstract

The electronic structures of MZr4(PO4)(6) (M2+ = Ca2+, Sr2+) were calculated using the CASTEP and the band gaps for CaZr4(PO4)(6) and SrZr4(PO4)(6) can reach up to 4.30 and 4.45 eV, respectively. Eu2+ doped MZr4(PO4)(6) were prepared by solid-state reaction method. The XRD patterns, luminescence, decay curves and thermal quenching properties of the samples were investigated. The Eu2+ ion can be totally incorporated into MZr4(PO4)(6) forming complete solid solutions. M1-xEuxZr4(PO4)(6) (0.01 <= x <= 1) shows typical broad band emission in energy range from 1.91 to 3.11 eV originating from the 4f(6)5d(1) -> 4f(7)5d(0) transition of Eu2+. With increasing Eu2+ concentration, there is an abnormal blue-shift of the emission for CaZr4(PO4)6:Eu2+ due to the decreasing crystal field strength and Stokes shift. However, there is no significant change in the position of the emission spectra in Eu2+-activated SrZr4(PO4)(6). M0.97Eu0.03Zr4(PO4)(6) shows the abnormal blue shift with decreasing emission intensity as an increase in temperature. (C) 2015 Elsevier Masson SAS. All rights reserved.