Tunable white-light-emitting Sr2−xCaxNb2O7:Pr3+ phosphor by adjusting the concentration of Ca2+ ion

• The solid solution was formed with the introduction of Ca2+ into host lattice until x = 0.5.
• As x exceeded 1.5, the system came into being a solid solution of Sr2−xCaxNb2O7 again.
• With varying the content of Ca2+, Sr2−xCaxNb2O7:Pr3+ could give out white light.
• The experimental values of IVCT transitions of Sr2Nb2O7:Pr3+ and Ca2Nb2O7:Pr3+ fell in the theoretical values.

The photoluminescence (PL) properties of Sr2−xCaxNb2O7:Pr3+ were investigated in this study. The system exhibited three different states when Sr2+ ion was replaced by Ca2+ ion gradually. The excitation spectra showed the absorptions of the charge transfer (CT) transition of NbO67- and intervalence charge transfer (IVCT) transition of Pr3+ → Nb5+. The transitions from 3H4 to 3PJ (J = 0, 1, and 2) of Pr3+ were located at 452, 474, and 490 nm. The main excitation peak changed with the phase transformations. The PL spectra of Sr2−xCaxNb2O7:Pr3+ excited with 320 nm showed two intense regions in the wavelength of 480–517 nm (blue-green) and 585–640 nm (orange-red). With increasing content of Ca2+ ion, the orange-red band enhanced and the Commission International de l’Echairage (CIE) moved from blue-green to white and then to purple.