Structures, and Thermophysical Properties Characterizations of (La1-xHox)3NbO7 Solid Solutions as Thermal Barrier Coatings

Lin Chen,Qi Zheng,Jing Feng,Yitao Wang

doi:10.3389/fmats.2021.703098

Lin Chen, Qi Zheng + Show 2 more

Open Access

https://doi.org/10.3389/fmats.2021.703098

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Abstract

A sequence of (La1-xHox)3NbO7 solid solutions were fabricated in this work, which were studied as candidate for thermal insulation materials. The lattices were identified via XRD, when SEM and EDS were used to characterize the microstructures and element distributions. The results showed that the highest modulus, hardness, and toughness of (La1-xHox)3NbO7 were 196 GPa, 9.2 GPa, and 1.6 MPa m1/2, respectively, and they accorded with the mechanical property requirements. Also, a low thermal conductivity (1.06 W m−1 K−1) and high thermal expansion coefficients (TECs: 11.3 × 10−6 K−1) were simultaneously realized in (La3/6Ho3/6)3NbO7, at high temperatures. No phase transition was detected up to 1,200°C, which proved their good high-temperature lattice stability. The intense anharmonic lattice vibrations might contribute to the outstanding thermal properties of (La1-xHox)3NbO7 ceramics. The suitable modulus, high hardness, low thermal conductivity, and high TECs of (La1-xHox)3NbO7 solid solutions proclaimed that they were exceptional thermal insulation ceramics.

Highlights

145.53 7.98 2.2 normalized XRD peaks of prepared specimens are depicted in Figure 1, and it is found that three types of lattices are formed
The main XRD peaks shift to the right along with the decline of La content displayed in Figure 1B, which indicates the shrinkage of the lattice
Dense (La1-xHox)3NbO7 oxide bulks have been fabricated in this work, and their structures and thermophysical properties are characterized

Summary

Introduction

Diverse oxide ceramics are studied as candidate for thermal barrier coatings (TBCs), which are used to reduce the temperatures of superalloy parts (Padture et al, 2002; Clarke, 2003; Chen et al, 2011; Zhang et al, 2016; Zhang et al, 2017; Chen et al, 2018a; Liu et al, 2018; Chen et al, 2019a; Chen and Feng, 2019; Liu et al, 2019; Zhang et al, 2019; Zhou et al, 2019; Zhang et al, 2020; Zhou et al, 2020; Zhou et al, 2021). Yttria-stabilized zirconia (YSZ) ceramics are widely researched and applied as TBCs, and they have good comprehensive thermophysical properties, including high hardness and fracture toughness, comparatively low thermal conductivity, and low density (Padture et al, 2002; Clarke, 2003; Chen et al, 2011). La2Ce2O7, LnMgAl11O19, La2Zr2O7, and other oxides are extensively researched as TBCs to replace YSZ, and low thermal conductivity, high hardness, and good lattice stability are found in some oxides (Wang et al, 2012; Yang et al, 2016; Zhang et al, 2016; Zhang et al, 2017; Chen et al, 2019a; Liu et al, 2019).

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