Structure and photoluminescence properties of rare-earth free narrow-band red-emitting Mg6ZnGeGa2O12: Mn4+ phosphor excited by NUV light

A kind novel red emission Mg6ZnGeGa2O12: Mn4+ phosphor under NUV excitation is synthesized successfully by high temperature solid-state reaction. The structure of Mg6ZnGeGa2O12 is investigated by TEM and X-ray powder diffraction (XRD) Rietveld Refinement; the luminescence properties are measured by diffuse reflection spectra, emission spectra, excitation spectra, decay curves and temperature dependence spectra. The result indicated that it has one octahedral site and tetrahedral site in crystal structure. Mn4+ can occupy octahedral (Mg2+(Zn2+)/Ga3+) site. It can emit red light peaking at 660 nm under NUV (420 nm) excitation. The critical quenching concentration of Mn4+ was about 1.0 mol%. The concentration quenching mechanism investigates to be a d-d interaction for the Mn4+ center. The CIE chromaticity coordinates and FWHM are (0.717, 0.283) and 25 nm. The PL intensity of Mg6ZnGeGa2O12: 1.0%Mn4+ drops to 75% when the temperature is raised up to 150 °C. It implies that Mg6ZnGeGa2O12: Mn4+ is a potential red phosphor matching NUV LED chips.