A novel reddish-orange emitting NaSrBiTeO₆:Sm³⁺ phosphor with high moisture resistance and thermostability for horticultural light emitting diode applications

A sequence of reddish-orange emitting NaSrBi(1-x)TeO6:xSm(3+) phosphors were successfully composited by a favorable solid-phase chemical process. The sintering temperature is optimized as 850 degrees C. NaSrBiTeO6 (NSBTO):Sm3+ samples were assigned to the cubic double-perovskite structure, exhibiting the space group of Fm3m (225). Photoluminescence emission spectra display the main peaks at 562, 598, 645, and 705 nm at 404 nm excitation. Among them, the most intense emission peak is at 645 nm. The concentration-quenching mechanism of Sm3+ follows the interaction between electric dipoles and quadrupoles. The asymmetric ratio (I((4)G(5/2)-H-6(9/2))/I((4)G(5/2)-H-6(5/2)) of NSBTO:2 mol%Sm3+ phosphor is extracted as 4.96. The optimum NSBTO:2 mol%Sm3+ phosphor has excellent thermal stability with a remained emission intensity riches 93.61% (420 K). After testing with high-pressure water steam at various periods, the phosphor remains chemically stable for moisture resistance. For the NSBTO:2 mol%Sm3+ phosphor, the satisfactory color purity and low correlated color temperature (CCT) are obtained with 99.9% and 1494 K, respectively. The electroluminescence spectra of the prepared red light emitting diode (LED) are in conformity with the phytochrome absorption spectra of chlorophyll a, chlorophyll b, P-FR, and P-R. The white light-emitting diode (w-LED) is also perfectly packaged, obtaining an efficient color rendering index (R-a) of 92.12 and CCT of 5553 K. These exceeding optical properties certified that NaSrBi(1-x)TeO6:xSm(3+) demonstrates promising prospects and can be efficiently applied in horticultural LED applications.