Thermal radiative properties of (La1−xSrx)MnO3−δ thin films fabricated on yttria-stabilized zirconia single-crystal substrate by pulsed laser deposition
For application as a variable thermal emittance material in a recently-developed thermal control system forspacecraft, (La1 − xSrx)MnO3 − δ (LSMO) thin filmswith thicknesses of 1.2 μm, 2.5 μm, and 4.3 μmwere fabricatedon yttria-stabilized zirconia (100) substrates by a pulsed laser deposition and ex-situ annealing at 1123 K in air.All the films were dense and their surface roughness was much smaller than the thermal infrared (IR) wavelength.The films had (100) and (110)-preferred orientations, and the thicker films showed more preferablegrowth along the (100) orientation. Temperature–magnetization curves revealed that the LSMO films exhibitedametal–insulator transition near roomtemperature. The thermal emittance of the films estimated fromIR reflectancespectra and black body radiation spectra exhibited large non-linearity near roomtemperature owing to thephase transition. The change in thermal emittance of the LSMOfilms thatweremore than 2.5 μmthickwas comparablewiththat of the Ca-doped LSMOceramic tiles already used as variable thermalemittancematerials. Thus,this result clearly demonstrates that LSMO thin filmswith thickness of 2.5 μmcanwork as variable thermal emittancematerials in the thermal control system for spacecraft.
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