Luminescent properties, energy transfer, and thermal stability of double perovskites La₂MgTiO₆:Sm³⁺, Eu³⁺

La₂MgTiO₆ red phosphors doped with both Sm³⁺ and Eu³⁺ were prepared by high temperature solid state method. Their phase compositions, morphologies, fluorescence spectra, fluorescence lifetimes and thermal stability were analyzed by X-ray diffraction, scanning electron microscopy, and fluorescence spectroscopy. The optimal synthetic temperature of La₂MgTiO₆:Sm³⁺, Eu³⁺ phosphors was 1400 °C. La₂MgTiO₆:Eu³⁺ showed red emission at 615 nm under 396 nm excitation, while La₂MgTiO₆:Sm³⁺ showed red orange emission at 601 nm under 406 nm excitation. La₂MgTiO₆: Sm³⁺, Eu³⁺ phosphor showed strong red emission at 615 nm under the excitation of 406 nm. The energy transfer from Sm³⁺ to Eu³⁺ in La₂MgTiO₆: Sm³⁺, Eu³⁺ was very effective. The maximum energy transfer efficiency was about 73.5% when Eu³⁺ concentration was 0.2. The temperature dependent emission spectra showed that the phosphors had good thermal stability. The La_1.94MgTiO₆:0.06Sm³⁺, La_1.85MgTiO₆:0.15Eu³⁺ and La_1.79MgTiO₆:0.06Sm³⁺, 0.15Eu³⁺ phosphors exhibited color purities close to 100%: 96.26%, 98.05% and 98.95%.