Comparison of the thermal resistance behaviour of synthesized Ln4Al2O9 (Ln = Y, Sm, Eu, Gd, Tb) materials vs commercial Zr0.8Y0.2O1.9 (8YSZ)

• Published in: Surface & coatings technology 2019-09, Vol.374, p.745-751
• Main Authors: Morán-Ruiz, Aroa, Wain-Martin, Aritza, Larrañaga, Aitor, Slater, Peter R., Arriortua, Maribel
• Format: Article
• Language: English
• Subjects: Aluminates; Ball milling; Chromium; Cuspidine-type rare earth aluminates; Gadolinium; Heat transfer; Interlayer materials for TBCs; Interlayers; Iron; Layer microstructure; Microstructure; Morphology; Porosity; Rare earth elements; Substrates; Synthesis; Thermal analysis; Thermal barrier coatings; Thermal energy; Thermal resistance; Thermal resistance capability; Yttria-stabilized zirconia; Yttrium oxide; Zirconium dioxide
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.06.070

Commercial yttria-stabilized zirconia Zr0.8Y0.2O1.9 (8YSZ), and five synthesized rare-earth aluminates Ln4Al2O9 (Ln = Y, Sm, Eu, Gd, Tb), were examined as possible intermediate-temperature barrier materials. The materials were directly deposited on preoxidized Fe-Cr metallic substrate, without bond coating as, using a wet colloidal spray technique. Phase purity and structures for all materials were confirmed by X-ray Diffraction (XRD) and the morphology of these compounds was examined using Scanning Electron Microscopy (SEM). The thermal resistance of the YSZ and Ln4Al2O9 (Ln = Y, Sm, Eu, Gd, Tb) layers was compared by the temperature drop method (∆T = Tsubstrate-Tsubstrate with coating), using an in-house built set up. Prior to measurement, the reproducibility and stability of the proposed experiment was confirmed. For the Eu4Al2O9 and Tb4Al2O9 coatings with thicknesses near 60 μm, the thermal resistance capability (≈180 °C) at 800 °C, was similar to that of the 8YSZ coating (commercial material for Thermal Barrier Coating (TBC) development). The cross-sectional microstructure of the samples, after thermal analysis was also examined, confirming no changes in the microstructure. Given the observed high thermal resistance capability values for the Ln4Al2O9 (Ln = Y, Sm, Eu, Gd, Tb) samples, and the possibility to change the porosity of the starting materials by ball milling, the results suggest that these materials have good potential for use as ceramic interlayers for TBCs. •Thermal resistance capabilities of 8YSZ and prepared Ln4Al2O9 coatings were studied.•To measure the temperature drop across TBCs a reproducible house built setup was used.•Eu4Al2O9 and Tb4Al2O9 layers showed the best thermal resistance effect.