Combined Solid Solution Engineering Realizes Unprecedented Tunable Broad NIR Emission in Novel Sr 1– z Ba z GeTeO 6 :Mn 4+ ( z = 0–1) Phosphors toward Noninvasive Temperature Monitoring

In this work, novel Mn 4+ -activated Sr 1– z Ba z GeTeO 6:0.01 Mn 4+ ( z = 0–1) phosphors presented recorded broadband NIR emissions (fwhm >100 nm) peaking from 767 to 820 nm in 650 to 1000 nm, upon blue light excitations with increasing z, corresponding to the rare spin-allowed 4 T 2g → 4 A 2g transition of Mn 4+ in a [GeO 6 ] octahedron, which originates from the proposed combined solid solution engineering in this system for the first time. Moreover, temperature sensing performance based on fluorescence lifetime mode is discussed for various samples, showing the maximal relative sensitivity S r = 3.01% K –1 @398 K in a mixed solid solution phase of Sr 0.6 Ba 0.4 GeTeO 6:0.01 Mn 4+ . Finally, a film involving a Sr 0.4 Ba 0.6 GeTeO 6:0.01 Mn 4+ phosphor was prepared to use for noninvasive temperature detection in a pork slice. Most encouragingly, this work strongly opens a chapter for finding novel Mn 4+ -activated broadband NIR-emitting phosphors with tunable emission wavelength over a large range.