Rare‐Earth‐Free High‐Efficiency Narrow‐Band Red‐Emitting Mg3Ga2GeO8:Mn4+ Phosphor Excited by Near‐UV Light for White‐Light‐Emitting Diodes.

A series of novel red emission Mg3Ga2GeO8 (MGG):Mn4+ phosphors under near-UV (NUV) excitation are synthesized successfully by traditional high-temperature solid-state reaction. The structure of Mg3Ga2GeO8 is investigated by high-resolution transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction (XRD) Rietveld refinement. It has one octahedral site and one tetrahedral site in the crystal structure. According to XRD and photoluminescence (PL) property analysis, Mn4+ can occupy an octahedral (Mg2+/Ga3+) site. The PL properties are investigated by diffuse-reflectance, emission, excitation, and temperature-dependent spectroscopy and decay curves. It can emit red light peaking at 659 nm under NUV excitation. The critical quenching concentration of Mn4+ was about 0.5 mol %. The concentration quenching mechanism could be a d–d interaction for the Mn4+ center. The CIE chromaticity coordinates and full-width at half-maximum are (0.295, 0.677) and 24 nm, respectively. It demonstr...