Thermophysical properties of weberite-type niobate Pr3NbO7 as a candidate TBC material

Searching oxides with a low thermal conductivity is important for the development and applications of thermal barrier coatings (TBCs), and RE₃MO₇ (RE = rare-earth elements; and M = Ta or Nb) oxides are studied as novel TBC materials in recent years. This work reports the thermophysical properties of weberite-type Pr₃NbO₇ niobates synthesized using a solid-state reaction, and its thermal and elastic properties are the key points. It is revealed that Pr₃NbO₇ has characteristics of a low thermal conductivity (k = 1.05 W m⁻¹ K⁻¹ at 900°C) and Young's modulus (E = 106 GPa), and its thermal expansion coefficients (TECs) are 8.9 × 10⁻⁶ K⁻¹ at 1200°C. The low thermal conductivity is related to its weberite-type structure and the differences of bonding strength between the Pr–O and Nb–O bonds, which can enhance the phonon scattering rate (E/k ratio) to reduce thermal conductivity. The modulus is mainly affected by the bonding strength, which is indicated by the Debye temperature (315 K), and modulus increases with the increasing Debye temperature for weberite-type RE₃MO₇ ceramics. The low thermal conductivity and modulus, as well as an excellent high-temperature stability prove that Pr₃NbO₇ is a promising candidate for TBC applications.