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

Abstract A series novel far-red emitting Ca2GdSbO6 (CGSO):xMn4+ 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 CGSO:0.003Mn4+ 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 Ca2(1-y)Sr2yGdSb0.997O6:0.003Mn4+. 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 CGSO:0.003Mn4+ 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.