Preparation, mechanical, and thermal properties of a promising thermal barrier material: Y4Al2O9

Yanchun Zhou,Huimin Xiang,Zhihai Feng,Xinpo Lu

doi:10.1007/s40145-015-0141-5

Abstract

In our previous work, anisotropic chemical bonding, low shear deformation resistance, damage tolerance ability, low thermal conductivity, and moderate thermal expansion coefficient of Y4Al2O9 (YAM) were predicted. In this work, phase-pure YAM powders were synthesized by solid-state reaction between Y2O3 and Al2O3 and bulk YAM ceramics were prepared by hot-pressing method. Lattice parameters and a new set of X-ray powder diffraction data were obtained by Rietveld refinement. The mechanical and thermal properties of dense YAM ceramics were investigated. The measured elastic moduli are close to the theoretical predicted values and the stiffness can be maintained up to 1400 ℃. The flexural strength and fracture toughness are 252.1±7.3 MPa and 3.36±0.20 MPa·m 1/2 , respectively. Damage tolerance of YAM was also experimentally proved. The measured average linear thermal expansion coefficient (TEC) of YAM is 7.37×10 6 K 1 , which is very close to the theoretical predicted value. Using high-temperature X-ray diffraction (XRD) analysis, volumetric TEC is determined (23.37±1.61)×10 6 K 1 and the anisotropic TEC are a = 7.34×10 6 K 1 , b = 7.54×10 6 K 1 , and c = 7.61×10 6 K 1 .

Highlights

Previous theoretical [1,2,3] and experimental [4,5] investigations have demonstrated that Y4Al2O9 (YAM) has a unique combination of high melting point (2020 °C), low density (4.44 g/cm3), low high-temperature thermal conductivity, relative low Young’s modulus (191 GPa), and moderate thermal expansion coefficient (7.51 × 10 6 K 1) and damage tolerant ability, which endure it as a prospective
The average linear thermal expansion coefficient (TEC) was measured by using an optical dilatometer, and the anisotropic thermal expansion coefficients at different directions were determined by high-temperature X-ray diffraction
One can see from the figure that the as-prepared YAM is phase-pure without any impurities detectable by X-ray diffraction (XRD)

Summary

Introduction

J Adv Ceram 2015, 4(2): 94–102 experimental determined lattice parameters and mechanical and thermal properties of dense phase-pure YAM. To achieve such a goal, single-phase YAM powders were prepared by solid-state reaction between Y2O3 and Al2O3 first. The average linear thermal expansion coefficient (TEC) was measured by using an optical dilatometer, and the anisotropic thermal expansion coefficients at different directions were determined by high-temperature X-ray diffraction. The Vickers hardness, flexural strength, fracture toughness, and dynamic Young’s modulus were measured. These fundamental data are helpful for promoting the applications of YAM as a TBC material or high-temperature structural component

Objectives

Methods

Results

Conclusion