In-situ synthesis of gadolinium niobate quasi-binary composites with balanced mechanical and thermal properties for thermal barrier coatings

Abstract

Yttria-stabilized zirconia (YSZ) has been used as a thermal barrier coating (TBC) material in gas turbines for several decades. Although continuous efforts have been made to develop novel TBC materials that can work at a higher temperature, no single material other than YSZ has all the desired attributes for the TBCs. In this paper, we report the in-situ synthesis of quasi-binary GdNbO4/Gd3NbO7 composites based on the simple Gd2O3-Nb2O5 binary phase diagram. The fracture toughness of these quasi-binary composites is remarkably enhanced compared with the value predicted by the rule of mixtures because the ferroelastic domain switching is more activated due to the residual stress in the quasi-binary composites, which triggers more crack defections due to the enlarged process zone. Additionally, the Gd3NbO7 phase provides a low thermal conductivity due to the substantial chemical inhomogeneity, which diffuses phonons. Gd3NbO7/GdNbO4 exhibits a balanced thermal conductivity of 1.6 W/(m·K) at 1073 K and a toughness value of 2.76 MPa·m0.5, and these values are among the best comprehensive properties that have been obtained for new TBC materials. The work demonstrates a feasible approach of designing a new TBC material with balanced properties and can be easily fabricated.

The modulated oxygen evolution reaction performance of LaFeO3 with abundant electronic structures via a design of stoichiometry offset

“…However, it is noted that the saturated magnetization can be greatly tuned by the stoichiometric offset. [57][58][59][60][61][62] Fig. 4(b) depicts the relationship curve of saturation magnetization (M s ) with oxygen pressure, which is quite similar to the OER performance of LFO.…”

Alternative Materials for Performant TBCs: Short Review

“…Therefore, more demanding performances are required to this technology, and there will be a continuing need to develop more durable TBCs. A numerous works on various aspects are found in the literature [12,13,[16][17][18][19][20][21][22][23].…”

Ferroelastic rare‐earth tantalates for multifunctional thermal/environmental barrier coatings: A perspective

“…44 YTaO 4 crystallizes into a tetragonal (t) phase at high temperatures (>1430 • C), and it transforms into a monoclinic (m) phase during cooling. [56][57][58][59][60][61][62] The t-m phase transition is achieved through a slight rotation/movement of atoms, as evidenced by the diffusive ferroelastic boundary shown in Figure 4(b)-(e). 21 Furthermore, the changes in TECs before and after the t-m phase transition are continuous, unlike in the case of YSZ.…”

“…In recent years, researchers have proposed the concept of multifunctional thermal/environmental barrier coatings (T/EBCs), designed to protect CMCs and alloy substrates from damage by high-temperature air, steam, and CMAS, while also providing sufficient thermal insulation performance. [53][54][55][56][57] Thus, ideal T/EBCs should exhibit low thermal conductivity, TECs matching to those of substrates, excellent resistance to CMAS and steam, and a low oxygen transport efficiency. Furthermore, high hardness and toughness and a relatively low Young's modulus are beneficial for extending the life span of T/EBCs.…”

“…Because many research papers and reviews have covered the progress of YSZ and rare‐earth (RE) silicates, 3,8,9,11,12,50,52 we will not describe their advantages and disadvantages in detail here. In recent years, researchers have proposed the concept of multifunctional thermal/environmental barrier coatings (T/EBCs), designed to protect CMCs and alloy substrates from damage by high‐temperature air, steam, and CMAS, while also providing sufficient thermal insulation performance 53–57 . Thus, ideal T/EBCs should exhibit low thermal conductivity, TECs matching to those of substrates, excellent resistance to CMAS and steam, and a low oxygen transport efficiency.…”