A novel multifunctional Eu3+/Mn4+ co-doping double perovskite phosphor for applications in LEDs and optical thermometry.

• The La 3 Mg 2 NbO 9 :Eu3+,Mn4+ phosphors with dual emission centers were synthesized by solid-state reaction method. • The crystal structure, morphology and luminous performance of La 3 Mg 2 NbO 9 :Eu3+,Mn4+were systematically analyzed. • The s r values of La 3 Mg 2 NbO 9 :Eu3+,Mn4+ sample reach 2.7 % K-1 (@478 K) based on the FIR mode and 5.2 % K −1 (@428 K) based on FIR mode. • The prepared red and white pc-LEDs show excellent performance in plant lighting lamps and WLEDs. In recent years, phosphors have played important roles in solid-state lighting, plant growth lighting and optical temperature measurement. In this work, novel La 3 Mg 2 NbO 9 :Eu3+,Mn4+ phosphors were successfully prepared by the high temperature solid phase method and innovative multimode applications were investigated in optical thermometry, plant growth and White-LEDs. The crystal structure, surface morphology, photoluminescence, temperature sensing properties and luminescence mechanism of La 3 Mg 2 NbO 9 :Eu3+,Mn4+ phosphors were investigated in detail. Benefiting from the different responses of Eu3+ and Mn4+ ions to temperature, the La 3 Mg 2 NbO 9 :0.06Eu3+,0.0095Mn4+ sample shows excellent optical thermometry performance in the range of 303 ∼ 478 K. The maximum values of relative sensitivity (S r) reach 2.7 % K-1 (@478 K) according to the fluorescence intensity ratio method and the maximum of S r is 5.2 % K −1 (@428 K) based on the fluorescence lifetime method. Furthermore, the electrochromic spectrum of the red pc-LED prepared using La 3 Mg 2 NbO 9 :0.06Eu3+,0.005Mn4+ phosphor perfectly overlapped with the absorption bands of the photosensitive pigments for planting, and another white pc-LED prepared using La 3 Mg 2 NbO 9 :0.06Eu3+,0.0025Mn4+ phosphor emitted bright white light with a color rendering index of 89.8, color coordinate of (0.3468, 0.3557) and correlated color temperature of 4945 K. All the results demonstrate that the La 3 Mg 2 NbO 9 :Eu3+,Mn4+phosphors are promising for the field of non-contact optical temperature thermometry, plant lighting lamps and pc-LED backlit displays. [ABSTRACT FROM AUTHOR]