Influence of Cation Substitution and Activator Site Exchange on the Photoluminescence Properties of Eu3+-Doped Quaternary Pyrochlore Oxides

Stannate-based pyrochlore-type red phosphors CaGd1–xSnNbO7:xEu3+, Ca1–ySryGd1–xSnNbO7:xEu3+, and Ca0.8–xSr0.2GdSnNbO7+δ: xEu3+ were prepared via conventional solid-state method. Influence of cation substitution and activator site control on the photoluminescence properties of these phosphors are elucidated using powder X-ray diffraction, Rietveld analysis, Raman spectrum analysis, and photoluminescence excitation and emission spectra. The Eu3+ luminescence in quaternary pyrochlore lattice exemplifies as a very good structural probe for the detection of short-range disorder in the lattice, which otherwise is not detected by normal powder X-ray diffraction technique. The Eu3+ emission due to magnetic dipole transition (5D0–7F1 MD) is modified with the increase in europium concentration in the quaternary pyrochlore red phosphors. 5D0–7F1 MD transition splitting is not observable for low Eu3+ doping because of the short-range disorder in the pyrochlore lattice. Appearance of narrow peaks in Raman spectra conf...