Evaluation of the in-depth temperature sensing performance of Eu- and Dy-doped YSZ in air plasma sprayed thermal barrier coatings

Abstract

In-depth temperature sensing in air plasma sprayed (APS) thermal barrier coatings (TBCs) has been achieved with europium (Eu) and dysprosium (Dy) doped yttria stabilized zirconia (YSZ) sensor coatings. The luminescence properties of YSZ:Eu and YSZ:Dy, including spectrum, intensity and lifetime, were evaluated and their temperature sensing performances were compared using a lifetime-based measurement system. Both sensor TBCs display excellent temperature sensitivity in high temperature environment (400-800 °C for YSZ:Eu, 500-900 °C for YSZ:Dy) with a topcoat thickness up to 300 m. It was found that the upper limit of temperature sensing was determined by the ratio between luminescence intensity and background thermal radiation (signal-background-ratio). YSZ:Dy showed higher luminescent intensity than YSZ:Eu at elevated temperatures, and therefore displayed better temperature sensing performance with an increased limit. The effect of topcoat thickness on the temperature sensing performance was also evaluated, showing that the attenuation factor of YSZ increased significantly with topcoat thickness. * Corresponding author Tel./fax: +8621 54742561. E-mail address: xiaofengzhao@sjtu.edu.cn (Xiaofeng Zhao). 2Interestingly, it was found that the topcoat attenuation factor gradually decreased as temperature increased, which improved the temperature sensing performance of sensor TBCs at elevated temperature. The findings in the temperature sensing of APS TBCs provide basis for the future development of on-line APS TBCs temperature monitoring technology.

“Oxygen quenching” in Eu-based thermographic phosphors: Mechanism and potential application in oxygen/pressure sensing

“…Therefore, the oxygen vacancy concentration in the lattice is hardly changed with the ambient gas. Considering that the high oxygen ionic conductivity due to the presence of a large number of oxygen vacancies [26] and the translucent nature of the ceramic YSZ to the visible light [5,7], it is not only the oxygen vacancies on the surface of the phosphor layer that should be considered, but also those in the inner part.…”

“…After being excited with a pulsed light, the phosphors exhibit exponentially decaying luminescence, and the decay time decreases as temperature increases. One of the recent applications of thermographic phosphor is the in-situ temperature measurement in thermal barrier coatings (TBCs) used in gas turbines [4][5][6]. During gas turbine services as well as in many other applications of combustion engines, motors or generators, it is very likely that the thermographic phosphors could be exposed to varied oxygen concentrations and surface pressures.…”

Assessment of the performance of Y2SiO5-YSZ/YSZ double-layered thermal barrier coatings

“…5b). No other phases or phase transformation can be detected [22,23]. However, for the pure Y2SiO5 top coat, a small broad peak at 28°-32° was observed in the as-sprayed coatings.…”

On the thermal sensitivity and resolution of a YSZ:Er3+/YSZ:Eu3+ fluorescent thermal history sensor

“…In terms of practical applications of YSZ:Er 3+ /YSZ:Eu 3+ coatings, it is expected that small thickness effects on the fluorescence intensity caused by coatings inhomogeneity and the variation of the viewing angle problem would be easily overcome by the use of an intensity ratio approach from Er 3+ and Eu 3+ emissions. Optical data (transmission, reflection, absorption, scattering) available in the literature for air-plasma sprayed and EB-PVD YSZ coatings [43][44][45][46], and from an earlier work for sol-gel deposited YSZ coatings [26] shows that the relative difference in absorption at the wavelength of Er 3+ green emissions (545 nm) and of Eu 3+ red emissions (606 nm) should be comprised between 5% and 20%. Therefore, the intensity ratio R(T) built from the green thermal history sensitive emission of Er 3+ ions and the red thermally insensitive emission of Eu 3+ ions (Eq.…”