Controlling the nanostructure and thermal properties of double-perovskite rare-earth tantalates by elemental doping

• Published in: Scripta materialia 2022-03, Vol.210, p.114408, Article 114408
• Main Authors: Kawai, Emi, Matsudaira, Tsuneaki, Ogawa, Takafumi, Kawashima, Naoki, Fisher, Craig A.J., Yokoe, Daisaku, Kato, Takeharu, Kitaoka, Satoshi
• Format: Article
• Language: English
• Subjects: Cation-deficient double-perovskite oxide; Elemental doping; Nanostructure; Thermal barrier coating; Thermal conductivity
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/j.scriptamat.2021.114408

Controlling the complex nanostructures that often form in cation-deficient oxides may provide an effective way to tailor their thermophysical properties, but this remains a challenging task. We report a study of un-doped and Hf-doped YTa3O9 with a Y-deficient double-perovskite structure using high-temperature X-ray diffraction, electron diffraction, and small-angle X-ray scattering. Undoped YTa3O9 has an orthorhombic structure with 90° and 180° domain walls and stacking faults observed at the micro and nano levels at room temperature. It undergoes a phase transition to a tetragonal phase, with an associated volume change, at around 700 K. Doping of the materials with Hf successfully stabilizes a tetragonal phase that includes a superstructure with periodic distances of a few nanometers at room temperature. The thermal conductivity of Hf-doped YTa3O9 is lower than that of the undoped material, suggesting that the interfaces between nanodomains interfere with diffusive thermal transport. [Display omitted]