By UV irradiation, phosphors (luminescent materials) can be excited to emit phosphorescence. For many phosphor materials, the spectral composition and the lifetime of the phosphorescence are temperature-dependent. Therefore the temperature of the phosphor can therefore be determined from the decay time of the phosphorescence when short laser pulses are used for the excitation. If a substrate, for example a combustion chamber wall, is coated with a thin layer of phosphor, the surface temperature of the substrate can be measured by this method. Depending on the phosphor material a temperature range of up to approximately 1700 K is accessible.
This technique is applied in our institute to determine surface temperatures of burner and combustion chamber parts during operation. The results yield, for instance, information about heat transfer processes or heat loads of combustor walls.