Thermal properties of a prospective thermal barrier material: Yb 3 Al 5 O 12
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Huimin Xiang and Xin Sun Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China
Jiachen Liu and Feng Hou Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
Yanchun Zhoua) Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China (Received 19 July 2014; accepted 8 October 2014)
In this article, a comprehensive investigation on the thermal properties of Yb3Al5O12 is conducted, including Debye temperature, thermal expansion coefficient (TEC), thermal diffusivity, heat capacity, and thermal conductivity. The calculated Debye temperature of Yb3Al5O12 from the measured elastic properties is 625 K. The linear and volumetric thermal expansions of Yb3Al5O12 from 298 to 1273 K are (7.83 6 0.14) 106 and (23.74 6 0.42) 106 K1, respectively. The linear TEC of the polycrystalline bulk Yb3Al5O12 determined by dilatometer is (8.22 6 0.3) 106 K1. The measured thermal conductivities of Yb3Al5O12 are 4.67 and 2.05 W (m K)1, respectively, at 300 and 1400 K. The estimated minimum thermal conductivity, jmin, is 1.22 W (m K)1. The high temperature thermal conductivity is close to the evaluated jmin, which is lower than most commonly used thermal barrier coating (TBC) material such as Y2O3-stabilized-ZrO2 (YSZ). The unique combination of these properties renders Yb3Al5O12 being a very promising candidate material for TBC. I. INTRODUCTION
The ability to perform and operate under harsh conditions that combine high temperatures, water vapor, as well as oxidative and corrosive environments significantly affects the efficiency and power of gas-turbine engines.1–4 Because the gas temperatures are typically higher than the melting point of metal substrate, protective thermal barrier coatings (TBCs) are required which can provide thermal insulation to metallic components from the hot gas environments. 5 Until now, Y 2O3 -stabilized-ZrO2 (YSZ) is the most commonly used TBC material.6–8 However, its working temperature is restricted because of phase transformation at high temperatures.9 Such phase transformations are usually accompanied by volume a)
Address all correspondence to this author. e-mail: [email protected], [email protected] This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/. DOI: 10.1557/jmr.2014.319 J. Mater. Res., Vol. 29, No. 22, Nov 28, 2014
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changes, which detract from the strain compatibility and reversibility of the coating.10 Additionally, the oxygen diffusivity of YSZ is high at elevated temperatures.11 Thus, searching for new TBC candidates is still needed. Pan et al.12 h
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