A new member of “114” family Ca1−x Eu x BaZn2+x Ga2−x O7 (x≤0.24): Structure and luminescence.

Abstract: New “114” oxides Ca1−x Eu x BaZn2+x Ga2−x O7 (x≤0.24) were synthesized by solid state reaction. Rietveld refinements were performed on high quality powder XRD data in the space group P63 mc. Zn2+ and Ga3+ co-occupy T1 and T2 positions, which are both in tetrahedral coordinated environment. Comparing the host compound, O3 moves towards T2 cation as much as 0.08Å when x=0.24. It is the most observable structural change during the substitution. By comparing the structures of CaBaZn2Ga2O7 (P63 mc) and CaBaCo4O7 (Pbn21), we find that smaller cations in tetrahedral sites would lead to a lower symmetry in “114” oxides. Luminescent spectra show the noncentrosymmetric coordination of Eu3+, and the f–f excitations are comparable to CT-excitation. No concentration quenching was observed up to x=0.24. The optical band gaps were estimated to be 3.8eV for Ca1−x Eu x BaZn2+x Ga2−x O7 (x=0, 0.16). [Copyright &y& Elsevier]