In the second year of this program on developing embedded optical sensors for thermal barrier coatings, our research has focused three topics: (i) Eu3+ doping for temperature sensing, (ii) the effect of long-term, high-temperature aging on the characteristics of the luminescence from the Eu3+ ions of 8YSZ materials, (iii) construction of a fiber-optic based luminescence detector system. It has been demonstrated that the variation in luminescence lifetime with temperature is identical for electron-beam evaporated Eudoped YSZ coatings as for bulk ceramics of the same composition. Experiments indicate that the luminescence lifetime method of measuring temperatures is sensitive up to 1150 degrees C for both Eu-doped YSZ coatings and Eu-doped Gd2Zr2O7. Furthermore, the technique is sensitive up to 1250 degrees C for the composition Eu2Zr2O7. The luminescence spectra Eu-doped YSZ are insensitive to long-term aging at high-temperatures, even to 195 hours at 1425 degrees C, except for a small frequency shift that is probably too small in measure except with instruments of the highest spectral resolution. The temperature of 1425 degrees C is much higher than present engines attain or even planned in the foreseeable future. Nevertheless, experiments are on-going to explore longer term exposures. A fiber-optic based luminescence system has been constructed in which the hottest section of fiber operates to at least 1250 degrees C.
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