Luminescence of Mn<sup>4+</sup> in a Hexafluorogermanate with the Complex Organic Cation Guanidinium [C(NH<sub>2</sub>)<sub>3</sub>]<sub>2</sub>GeF<sub>6</sub>:Mn<sup>4+</sup>
Florian Baur, David Böhnisch, Thomas Jüstel
Abstract
This work concerns the synthesis and optical characterization of a novel Mn 4+ activated luminescent material with chemical composition of [C(NH 2 ) 3 ] 2 GeF 6 :Mn 4+ . This is the first report of a Mn 4+ activated fluoride comprising organic moieties. X-ray diffraction, IR transmission, differential thermal analysis/thermogravimetry and inductively coupled plasma-mass spectrometry analyses were performed to investigate the properties of the phosphor. It turns out that the material is an efficient emitter at low temperature (3 K), but the luminescence is quenched at elevated temperature. This is a rare property for Mn 4+ activated fluorides and the reason for the low thermal quenching temperature is investigated. The emergence of a second zero phonon line is observed in emission spectra at temperatures higher than 10 K and a relation to spin–orbit coupling is shown. Thermal population of the higher spin–orbit level is investigated with theoretical and experimental means.