Far red-emitting double perovskite phosphors Ca2(1-x)Sr2xGdSbO6:Mn4+: Luminescence improvement based on composition modulation

A series novel far-red emitting Ca2GdSbO6(CGSO):xMn(4+) phosphors were prepared by traditional high temperature solid-state reaction method. The phase composition, morphology, element distribution and valence state of the phosphor were characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), respectively. The optimum doping concentration of Mn4+ is x = 0.003. When Ca2+ is gradually replaced by Sr2+, the emission intensity of CGS0:0.003Mn(4+) increases first and then decreases, and the photoluminescence emission (PL) spectra exhibit a significant red shift, which promotes the adjustability of the spectra. A small amount of Sr2+ doping can effectively improve the red emission intensity of Ca(2(1-y))Sr(2)yGdSb(0.997)O(6):0.003Mn(4+). When y = 0.2, the red emission of the phosphor reaches the maximum and can be stimulated by ultraviolet LED chip. Under the excitation of 332 nm, as-prepared CGS0:0.003Mn(4+) emits intense red light around 677 nm, and the quantum yield is as high as 33.92%. Besides, the thermal stability of samples was studied and discussed in detail at the first temperature cycle. The results not only validate that high performance Mn4+-actived far-red phosphors can be obtained by cation substitution, but also can guide the design of Mn4+ -actived phosphors in the future.