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

Highlights: • A color-tunable dual-emitting La₂LiSbO₆:Bi³⁺, Sm³⁺ phosphor was firstly prepared. • Its potential application in WLED and optical thermometry was appraised. • ET process between Bi³⁺ and Sm³⁺ ions was observed and its mechanism was analyzed. • The ET process has led to colcor-tunable emissions and increased the quantum yields of Sm³⁺ in La₂LiSbO₆:Bi³⁺, Sm³⁺. • La₂LiSbO₆:Bi³⁺, Sm³⁺ has exhibited excellent optical sensitivity to temperatures with a large relative sensitivity. 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 (S_r) 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.