Characterization of manganese-activated magnesium fluorogermanate with regards to thermographic phosphor thermometry

Apart from the temperature, four parameters were investigated for their impact on the phosphorescence characteristics of Mg4FGeO6:Mn with regards to phosphor thermometry: the dopant concentration, the laser pulse energy, gas compositional and pressure effects as well as irreversible changes due to heat treatments. Five specially produced phosphors with different dopant concentrations as well as commercially available Mg4FGeO6:Mn were investigated in the form of coatings and pure powder. The phosphorescence was excited by the third harmonic of a pulsed Nd:YAG laser (355 nm). The lifetime decay as well as the emission spectra of the subsequently emitted phosphorescence were determined. Generally, the decay time decreased with increasing dopant concentration, with increasing laser pulse energy and for coatings also with increasing maximum temperature and duration of heat treatments, whereas the impact of the laser power was minimized by a modified evaluation routine of the decay time. Gas compositional and pressure effects did not have a significant influence on the decay time of Mg4FGeO6:Mn. Neither the variation of the dopant concentration nor the exposure to heat treatments influenced the shape of the emission spectra in any way.