Phase Formation and Thermal Stability of Reactively Sputtered YTaO4–ZrO2 Coatings

• Published in: Materials Vol. 14; no. 3; p. 692
• Main Authors: Stelzer, Bastian, Pingen, Katrin, Hans, Marcus, Holzapfel, Damian M., Richter, Silvia, Mayer, Joachim, Pradeep, Konda Gokuldoss, Schneider, Jochen M.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 02.02.2021; MDPI
• Subjects: Aluminum oxide; Annealing; Coatings; Cooling; Energy; Grain size; Heat conductivity; Lasers; phase stability; Phase transitions; PVD; Room temperature; Substrates; Temperature; thermal barrier coatings; Thermal stability; Thin films; X-ray diffraction; yttrium tantalate; zirconia; Zirconium dioxide; United States > US; Japan
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma14030692

Y(1−x)/2Ta(1−x)/2ZrxO2 coatings with 0 to 44 mol% ZrO2 were synthesized by sputtering. Phase-pure M’-YTaO4 coatings were obtained at a substrate temperature of 900 °C. Alloying with ZrO2 resulted in the growth of M’ along with t-Zr(Y,Ta)O2 for ≤15 mol%, while for ≥28 mol%, ZrO2 X-ray diffraction (XRD) phase-pure metastable t was formed, which may be caused by small grain sizes and/or kinetic limitations. The former phase region transformed into M’ and M and the latter to an M’ + t and M + t phase region upon annealing to 1300 and 1650 °C, respectively. In addition to M and t, T-YTa(Zr)O4 phase fractions were observed at room temperature for ZrO2 contents ≥28 mol% after annealing to 1650 °C. T phase fractions increased during in situ heating XRD at 80 °C. At 1650 °C, a reaction with the α-Al2O3 substrate resulted in the formation of AlTaO4 and an Al-Ta-Y-O compound.