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 La1.94MgTiO6:0.06Sm3+, La1.85MgTiO6:0.15Eu3+ and La1.79MgTiO6:0.06Sm3+, 0.15Eu3+ phosphors exhibited color purities close to 100%: 96.26%, 98.05% and 98.95%.