Energy transfer and tunable-color luminescence properties of a single-phase CaSrNb2O7:Sm3+, Bi3+

Abstract

New tunable-color luminescent materials are getting a lot of attention. Double-doped activated ions are an important research method. Here, CaSrNb2O7:R3+ (R3+ = Sm3+, Bi3+, and Sm3+/Bi3+) are synthesized by solid state method in the air. Phase purity and successful synthesis of samples are confirmed by X-ray diffractometer (XRD) patterns and energy disperse spectroscopy (EDS) diagram. The luminescence properties of samples are studied. CaSrNb2O7:Sm3+ has an excitation spectrum due to the O2- - Sm3+ charge transfer band (CTB) and the 6H5/2 → 4H9/2, 4D3/2, 4D1/2, 4F7/2, and 4I11/2 transitions of Sm3+ ion. The red-orange emission of CaSrNb2O7:Sm3+ is observed because of the 4G5/2 → 6H5/2, 6H7/2, 6H9/2, and 6H11/2 transitions of Sm3+ ion. PLE spectrum of CaSrNb2O7:Bi3+ comes from the metal-to-metal charge- transfer (MMCT) Bi3+ - Nb5+ and the 1S0 → 1P1 and 3P1 transitions of Bi3+ ion. CaSrNb2O7:Bi3+ shows blue emission due to the 3P1 → 1S0 transition of Bi3+ ion. The excitation spectrum of CaSrNb2O7:Sm3+, Bi3+ contains that of CaSrNb2O7:Bi3+ and CaSrNb2O7:Sm3+. CaSrNb2O7:Sm3+, Bi3+ with excitation at 314, 363, and 406 nm glows orange and red-orange, and red emission, respectively. We observe the energy transfer from Bi3+ to Sm3+ ions and the effect of Bi3+ on luminescence properties of Sm3+ ion by their spectra. The optimal Sm3+ and Bi3+ concentrations are confirmed by the concentration dependent spectra. The energy level diagrams of Sm3+ and Bi3+ are used to analyze the luminous mechanism. The results are conducive to the development of new Sm3+ and Bi3+ co-doped luminescent materials.