Synthesis and characterization of Eu3+ doped CaZrO3-based perovskite type phosphors. part II: PL properties related to the two different dominant Eu3+ substitution sites

Eu3+-doped perovskite type CaZrO3-based phosphors were synthesized by the solid state reaction at 1400 °C for 6 h in air. To change the short range structure around Eu3+ in the CaZrO3-based compounds, two different cations were selected and co-doped; Sr2+ with a larger ionic radius compared with Ca2+ in the CaZrO3, and Mg2+ having a smaller one. According to the results obtained by our previous study, the chemical composition of the starting powder mixtures was controlled by taking into account of the dominant Eu3+ substitution site as A-site (Ca2+) for Ca1−xSrx−0.05ZrO3:Eu3+0.05 (x=0.2, 0.4), and that as B-site (Zr4+) for Ca1−yMgyZr0.95O3:Eu3+0.05 (y=0, 0.02, 0.04, 0.06, 0.08, 0.1). The results of the X-ray diffraction analysis revealed that Sr2+ mainly occupied the A-site as designed, and the lattice constants of the Ca1−xSrx−0.05ZrO3:Eu3+0.05 increased with increasing amount of the Sr2+-doping up to 35 mol% without secondary phase formation. Mg2+ substitution to Ca2+ at the A-site in the CaZr0.95O3:Eu3+0.05 could be also achieved. However, the maximum amount of Mg2+ in the CaZr0.95O3:Eu3+0.05 was found to be low, approximately 6 mol%. CaZr0.95O3:Eu3+0.05 showed characteristic emission of the Eu3+ (f-f transition) by CTB excitation. The intensity of the dominant PL emission peak centered at 614 nm (5D0 - 7F2) increased consistently with the amount of the Mg2+-doping, and the 6 mol% Mg2+-doped sample exhibited the highest emission peak intensity which was approximately 1.4 times higher than that of the Mg2+-free CaZr0.95O3:Eu3+0.05. On the other hand, the emission peak intensity at 614 nm decreased with increasing amount of the Sr2+-doping. The relationships between the PL emission properties and the material parameters such as lattice constants of the host CaZrO3-based compounds, dominant Eu3+ substitution site and the site symmetry around Eu3+ in the host lattice were discussed from a viewpoint to improve the PL red emission properties of the Eu3+-doped CaZrO3-based compounds.