Composition adjustment verifies structure-property correlation in narrow-band green-emitting Zn4-xMgxB6O13: Mn2+ phosphor

Abstract

A variety of optoelectronic devices such as photovoltaics and light-emitting diodes need stable performance of phosphors and the most important factor in liquid-crystal display (LCD) backlights will be the color purity. Here, a novel rare-earth-free narrow-band green-emitting phosphor based on the substitution of Mg2+ for Zn2+ in the lattice of Zn3.98-xMgxB6O13:0.02Mn2+ has been assembled via a solid-state reaction method. According to XRD and Rietveld refinement results, Zn3.98-xMgxB6O13:0.02Mn2+ can achieve perfect solid solution phases at 0 ≤ x ≤ 0.2 in terms of the same cubic structure of Zn4B6O13 with space group I-43m (217). Under the excitation at 450 nm in blue region, Zn3.98-xMgxB6O13:0.02Mn2+ phosphors possess the green emission band at λmax ~542 nm and its full-width at half-maximum (FWHM) has been found to be only 39 nm. In addition, the emission intensity can be enhanced by increasing Mg content (x) from 0 to 0.1. It has to be mentioned that the thermal stability for the composition-optimized x = 0.1 sample is superior to that of the unsubstituted sample (x = 0). The underlying mechanism for this luminescence improvement has been verified. By virtue of assembling a green-emitting Zn3·97Mg0·1B6O13:0.02Mn2+ phosphor and a commercial red-emitting K2SiF6:Mn4+ phosphor as light converters, a warm white light has been achieved based on InGaN-based blue-LED (450 nm) and such device gives rise to wide color gamut of 105% National Television System Committee (NTSC) and good color-rendering index Ra of 90.6 at a correlated color temperature of 3683 K. Our results pave a new way in developing Mn2+-activated thermally stable narrow-band green-emitting phosphors with improving luminescence performance by simple compositional adjustments.