Photoluminescence properties and crystal structure of color-tunable yellow–orange–carroty–red emissive Sr_2(1−x)Na_xP₂O₇:xSm³⁺ phosphors for near-UV/blue light-based white LEDs

A series of Sr_2(1−x)Na_xP₂O₇:xSm³⁺ phosphors with adjustable emission have been synthesized via one-step calcination process of the precursors prepared by co-precipitation method successfully. The crystal structure and luminescent properties of the phosphors were analyzed in detail. Because the Sm³⁺ could occupy two different types of Sites (Sr₁ and Sr₂), the emission spectra of the Sr_2−xP₂O₇:xSm³⁺ phosphors excited at 402 nm showed an emission band consisting of two symmetrical single bands (Em1 and Em2) in the wavelength range of 580–620 nm with a peak at 599 nm (⁴G_5/2 → ⁶H_7/2). The optimal doping concentration of these phosphors was at x = 0.04. The charge compensator Na⁺ ions can not only improve emission luminous intensity and quantum efficiency (QE) of the Sr₂P₂O₇:Sm³⁺, but also change the shape and position of the emission peak at 599 nm. The color tunable wide gamut light can be controlled through properly adjusting the excitation wavelength of obtained samples, covering the yellow, orange, carroty and red chromaticity region, indicating Sr_2(1−x)Na_xP₂O₇:xSm³⁺ phosphors have high absorptions from the near ultraviolet to blue region and can be efficiently excited by commercial NUV and blue LEDs, thus can be used for developing warm white LEDs.