Upconversion Phosphor Thermometry for use in Thermal Barrier Coatings

Abstract Measuring the temperature below surface of a thermal barrier coating (TBC) using thin phosphor layer is challenging primarily due to absorption and scattering laser excitation light luminescence as they propagate through coating. One way increase could be use upconversion thermometry, which investigated in current study. It attractive because longer wavelengths reduces TBCs 8 % wt. Yttria-Stabilize Zirconia (8YSZ) generally has lower coefficients around 1000 nm than at 532 355 nm. Therefore, viability measure bottom TBC was evaluated for first time compared with more conventional downconversion thermometry. The work involved an experimental study several phosphors lanthanides doped 8YSZ host, were excited by pulsed 965 light. YSZ:Er,Yb YSZ:Ho,Yb show promise experimentally acquired optical characteristics used simulate propagation Kubelka-Munk theory. This evaluate signal strength excitation. Upconversion resulted greater from embedded much higher lifetime thermometry also improved sensitivity. Coupled reduced interference background impurities upconversion, it promising method measurements thermographic or underneath TBC.