The characterization of Y2O2S : Sm powder as a thermographic phosphor for high temperature applications

Thermographic phosphors may be used to measure surface temperatures in host ile and high temperature environments and have applications in gas turbine combustors and high temperature regions of the turbine. Most phosphors are excited by UV light and exhibit a temperature sensitive exponential decay i n emission once excitation has ceased. This can be characterized using a ph otomultiplier enabling temperatures to be measured at discrete points on th e surface. However, one phosphor, YAG:Dy, is known to exhibit temperature s ensitivity in the relative intensity of specific lines in its emission spec trum. Emission intensity can be recorded as an image using a CCD camera and hence this type of response can lend to the measurement of surface tempera ture distributions. In the paper the energy level characteristics of Dy lea ding to the intensity ratio response are discussed. Another lanthanide, Sm, is shown to exhibit similar characteristics and has been experimentally in vestigated using Y2O2S:Sm powder. Y2O2S:Sm has been shown to exhibit intens ity ratio sensitivity over a temperature range from room temperature to 110 0 K and to be suitable for temperature measurement by this means with an un certainty of approximately +/-1%. It has also been shown to exhibit lifetim e decay sensitivity over the temperature range from 900 to 1425 K and to be suitable for temperature measurement by this means with an uncertainty of approximately +/-1%. In both cases the upper temperature limit is a functio n of the instrumentation used and the dynamic response may extend further. Decoy time constants for Y2O2S:Sm are very short (3 mu s at 1400K), compare d to those for YAG:Dy, making it suitable for use on moving surfaces by eit her response mode. This material, or other Sm doped phosphors, may therefor e be useful for surface temperature measurement on rotating turbine blades.