Synthesis and properties of Sm<sup>3+</sup> doped NaLa(WO<sub>4</sub>)<sub>2</sub> single matrix white phosphors

Abstract

<sec>Single ion doped single phase white emitting phosphors have some special advantages and great potential applications in the field of high quality LED lighting. This type of phosphors can effectively solve the problem of uneven particle dispersion and sedimentation in the white light scheme obtained by UV chip plus trichromatic phosphor, and solve the problems of the luminescence and reabsorption between phosphors and the regulation of trichromatic ratio. A comparison of the single-ion doping luminescent material with the multi-ion doping system shows that the single-ion doping luminescent material is simpler in both preparation process and luminescence color adjustment, which can achieve higher color rendering index, more easily controlled color temperature and closer to the color coordinates of white light. </sec><sec>According to the principle of colorimetry and luminescence, light of two or more wavelengths may be combined to obtain white light emission. Under the UV excitation, the Sm<sup>3+</sup> ions emit relatively strong green, yellow, orange and red light at 580–670 nm. Under UV excitation, the broadband spectrum of <inline-formula><tex-math id="Z-20210831172528">\begin{document}${\rm{WO}}_{4}^{2-} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210493_Z-20210831172528.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210493_Z-20210831172528.png"/></alternatives></inline-formula> self-activated emission covers almost the whole visible region, but the blue-green light is strong in the short wavelength region and the yellow-orange-red light is weak in the long wavelength region. When Sm<sup>3+</sup> ions are doped into tungstate, Sm<sup>3+</sup> ions’ luminescence can effectively supplement the weak luminescence intensity of tungstate in the long-wave region, and white light can be obtained. Under the excitation of 250 nm, the phosphor emits cold white light, and warm white light under the excitation of 403 nm. The experimental results show that Sm<sup>3+</sup> ions have a significant effect on the correlated color temperature adjustment of self-activated luminescence of NLW phosphors. All the prepared samples are crystallized into the tetragonal crystal phase structures and that their morphologies present rhombic sheet. By analyzing the experimental data, the type of energy transfer between Sm<sup>3+</sup> ions is determined to be electrical dipole–electrical dipole interaction. The NLW: <i>x</i>Sm<sup>3+</sup> phosphor has high stability and can be effectively excited by ultraviolet/near-ultraviolet light, which can be used as a potential candidate of single matrix single-ion doped white phosphors.</sec>