Color-tunable luminescence and temperature sensing properties of a single-phase dual-emitting La2LiSbO6:Bi3+, Sm3+ phosphor

Abstract

In this article, we present a systematic research on the structure, tunable luminescence and temperature sensing properties of Bi3+, Sm3+ singly/co-doped La2LiSbO6 phosphors, which were prepared via solid state reaction method. All the X-ray diffraction (XRD) patterns of prepared samples showed very good coincidence with the pure La2LiSbO6 and the accurate lattice parameters were refined using high-quality XRD data. Under near ultraviolet excitation, the La2LiSbO6:Bi3+ phosphor exhibits a broad blue-violet band corresponding to the 3P1 →1S0 transition of Bi3+ ions, whereas the La2LiSbO6:Sm3+ phosphor exhibits characteristic luminescence properties of Sm3+ with four emission bands in the reddish-orange region. The large overlap between the emission spectrum of Bi3+ and excitation spectrum of Sm3+ leads to efficient energy transfer (ET) from Bi3+ to Sm3+ ions, which is also demonstrated by the emission spectra and decay curves of Bi3+ in La2LiSbO6:Bi3+, Sm3+ phosphors. On the basis of the Dexter and Reifsfeld's theory, the critical distance for ET between Bi3+ and Sm3+ was calculated to be 12.05 Å and the ET mechanism was determined to be a dipole-dipole interaction. Furthermore, because of the huge discrepancy between the thermal quenching rates of Bi3+ and Sm3+, the La2LiSbO6:Bi3+, Sm3+ phosphor exhibits excellent optical sensitivity to temperatures with a large relative sensitivity (Sr) of 1.48%K−1. Finally, the potential application of the La2LiSbO6:Sm3+ phosphor in indoor illumination was also evaluated according to the photoelectric parameters of the fabricated LED.