Phosphor thermometry

Phosphors are fine white or pastel-colored inorganic powders which may be stimulated by any of a variety of means to luminesce, i.e. emit light.

Certain characteristics of the emitted light change with temperature, including brightness, color, and afterglow duration.

The first mention of temperature measurement utilizing a phosphor is in two patents originally filed in 1932 by Paul Neubert.

[1] Typically a short duration ultraviolet lamp or laser source illuminates the phosphor coating which in turn luminesces visibly.

For instance, there is a phase difference between a sinusoidally varying light-emitting diode (LED) signal of frequency f and the fluorescence that results (see figure).

Several observations are pertinent to the figure on the right: There are further parameters influencing the luminescence of thermographic phosphors, e.g. the excitation energy, the dopant concentration or the composition or the absolute pressure of the surrounding gas phase.

A thermal barrier coating (TBC) allows gas turbine components to survive higher temperatures in the hot section of engines, while having acceptable life times.

First work on industrial atmospheric plasma sprayed (APS) sensor coating systems commenced around 2002 and was published in 2005.

[12] They demonstrated the capabilities of APS sensor coatings for in-situ two-dimensional temperature measurements in burner rigs using a high speed camera system.

[14] Results on multilayer sensing TBCs, enabling simultaneous temperature measurements below and on the surface of the coating, were reported.

[15] While the previously mentioned methods are focusing on the temperature detection, the inclusion of phosphorescent materials into the thermal barrier coating can also work as a micro probe to detect the aging mechanisms or changes to other physical parameters that affect the local atomic surroundings of the optical active ion.

[8][16] Detection was demonstrated of hot corrosion processes in YSZ due to vanadium attack.