Stannate-based pyrochlore-type red phosphors CaGd1-xSnNbO7:xEu(3+), Ca1-ySryGd1-xSnNbO7:xEu(3+), and Ca0.8-xSr0.2GdSnNbO7+delta: xEu(3+) 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 (D-5(0)-F-7(1) MD) is modified with the increase in europium concentration in the quaternary pyrochlore red phosphors. D-5(0)-F-7(1) 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 confirms that short-range disorder in the crystal lattice disappears with progressive europium doping. By using Sr as a network modifier ion in place of Ca we were able to increase the f-f transition intensities and europium quenching concentration. The influence of effective positive charge of the central Eu3+ ions when it replaces a metal ion having lower oxidation state such as Ca2+ was also investigated. The relative intensities of A(1g) (similar to 500 cm(-1)) and F-2g (similar to 330 cm(-1)) Raman vibrational modes get inverted when Eu3+ ions replaces Ca2+ ions instead of Gd3+ as trivalent europium ions can attract the electron cloud of oxygen ions strongly in comparison with divalent calcium ions. The influence of positive charge effect of Eu3+ in Ca0.7Sr0.2GdSnNbO7+delta:0.1Eu(3+) phosphor is greatly strengthened the charge transfer band and F-7(0)-L-5(6) transition intensities than that of the Ca0.8Sr0.2Gd0.9SnNbO7:0.1Eu(3+) phosphor. Our results suggest that the photoluminescence properties can be enhanced by simple compositional adjustments in the quaternary pyrochlore-type red phosphors.