Effect of La2O3 on Microstructure and Thermal Conductivity of La2O3-Doped YSZ Coatings.

Xiaojie Guo,Yi Zeng,Wei Zheng,Jimei Zhang,Ziwei Liu,Chucheng Lin,Caifen Jiang

doi:10.3390/ma12182966

Abstract

Enhancing the properties of thermal barrier coatings (TBCs) by doping with rare earth elements has been a hot topic for a while. La2O3 and Y2O3 co-doped ZrO2 (La-YSZ) TBCs and yttria-stabilized zirconia (YSZ) TBCs were deposited by atmospheric plasma spraying (APS), and the comprehensive effects of La3+ on the microstructure and property were investigated. The thermal conductivity and microstructure were investigated and were compared with YSZ. The recrystallized fraction components of all TBCs were quantified. It is clearly found that the component of “recrystallized” and “deformed” grains for La-YSZ TBCs is much higher than that for YSZ TBCs. This could be due to La3+ doping enlarging the lattice parameter of YSZ and thus increasing the melting index, which in turns leads to the smaller grain size of La-YSZ TBCs. As a result, the thermal conductivities of La-YSZ TBCs were distinctly lower than those of YSZ TBCs.

Highlights

Yttrium oxide-stabilized zirconia (YSZ), a high-temperature structural material with low thermal conductivity and high thermal expansion, is widely used as a thermal barrier coating (TBC) [1,2,3]
The columnar grains were solidified from the melted fraction of La-yttria-stabilized zirconia (YSZ) powder and the spherical-similar microstructure was retained from the unmelted La-YSZ powder
The thickness of the splat and the width of the column grains of N1 are distinctly smaller than N4, which indicates that La-YSZ powder was at a better molten state when deposited on the substrate than YSZ powder

Summary

Introduction

Yttrium oxide-stabilized zirconia (YSZ), a high-temperature structural material with low thermal conductivity and high thermal expansion, is widely used as a thermal barrier coating (TBC) [1,2,3]. In addition to the Y2 O3 -ZrO2 (YSZ) TBCs, it has been found that lanthanum-doping can effectively reduce the thermal conductivity of YSZ TBCs. It has been reported that La2 O3 and Y2 O3 co-doped. It was reported that the grain growth of coatings under high temperatures can be improved by the addition of La2 O3. Of Laincreases causedthe thinner splats and smaller grains This number of interfaces, thereby enhancing phonon the scattering and, a result, reduces enhancing phonon scattering and, as a result, reduces thermal conductivity [16]. For YSZ coatings, of microstructure microstructure on the thermal has been studied extensively using the electron the thermal conductivity has beenconductivity studied extensively using the electron back-scattered diffraction back-scattered (EBSD).

Materials

Microstructures of Coatings

Thermal Conductivity Measurements

Morphology and Phase Analysis

Thermal Conductivity of Coatings

Conclusion