Ce1−x Sm x O2−x/2—A novel type of ceramic material for thermal barrier coatings

Journal of Advanced Ceramics, Jul 2016

In this study, Ce1−x Sm x O2−x/2 ceramics were synthesized by sol–gel route and solid state sintering method. The phase structure was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The morphologies of the synthesized powders and the corresponding bulk samples were observed using scanning electron microscopy (SEM). Their thermal diffusivities and thermal expansion coefficients were measured by the laser-flash method and the pushing-rod method, respectively. Results show that pure Ce1−x Sm x O2−x/2 powders with single fluorite structure are synthesized successfully, and their microstructures of the corresponding bulk samples are very dense. With the increase of Sm2O3 content, their thermal expansion coefficients decrease due to the higher electro-negativity of Sm3+ ions as compared with that of Ce4+ ions. Their thermal conductivities at 1000 °C lie in the range of 1.62–2.02 W/(m·K) due to the phonon scattering caused by the substituted atoms and oxygen vacancies. The Ce1−x Sm x O2−x/2 ceramics can be used as ceramic candidates for novel thermal barrier coatings (TBCs).

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Ce1−x Sm x O2−x/2—A novel type of ceramic material for thermal barrier coatings

Journal of Advanced Ceramics 2226-4108 Ce1xSmxO2x/2-A novel type of ceramic material    for thermal barrier coatings Xiao-ge CHEN Haoming ZHANG Hong-song ZHANG 0 1 a b Yong-de ZHAO Gang LI 0 c 0 Department of Mechanical Engineering, Henan Institute of Engineering , Zhengzhou 450007 , China 1 Institute of Chemistry Henan Academy Sciences , Zhengzhou 450052 , China 2 Department of Construction Engineering, Henan Institute of Engineering , Zhengzhou 450007 , China In this study, Ce1xSmxO2x/2 ceramics were synthesized by sol-gel route and solid state sintering method. The phase structure was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The morphologies of the synthesized powders and the corresponding bulk samples were observed using scanning electron microscopy (SEM). Their thermal diffusivities and thermal expansion coefficients were measured by the laser-flash method and the pushing-rod method, respectively. Results show that pure Ce1xSmxO2x/2 powders with single fluorite structure are synthesized successfully, and their microstructures of the corresponding bulk samples are very dense. With the increase of Sm2O3 content, their thermal expansion coefficients decrease due to the higher electro-negativity of Sm3+ ions as compared with that of Ce4+ ions. Their thermal conductivities at 1000 ℃ lie in the range of 1.62-2.02 W/(m·K) due to the phonon scattering caused by the substituted atoms and oxygen vacancies. The Ce1xSmxO2x/2 ceramics can be used as ceramic candidates for novel thermal barrier coatings (TBCs). thermal barrier coatings (TBCs); CeO2 oxides; doping; thermophyscial properties - properties, 7–8 wt% yttria-stabilized zirconia (YSZ) ceramic has been widely employed as the top coat material by the current commercial thermal barrier coatings in high temperature turbine components. However, the thermal insulation ability and working lifetime of the YSZ thermal barrier coating can be injured severely for long-term application above 1200 ℃ due to its inherent phase transformation and enhanced sintering [5,6]. Therefore, it is very urgent to develop alternatives to YSZ for advanced TBC applications. The excellent ceramic candidates for TBCs must possess a few important performances, such as low thermal conductivity, appropriate thermal expansion, good phase stability at high temperature, low sintering rate, high melting point, chemical inertness, and good adherence to the metal substrate [7]. However, ceramic materials matching all the requirements are still very rare in light of the current standard. Now, low thermal conductivity and appropriate thermal expansion coefficient have been regarded as the primary selection criterions of the ceramic materials for TBC applications. In recent years, ceramic oxides with pyrochlore structure or defect fluorite structure have been widely studied [8–11]. Except for the A2B2O7-type (A = rare earth element, B = Zr, Ce, Hf, Sn) oxides [1–10], the cerium oxides with fluorite structure have recently attracted extensive attention due to a diversity of applications, such as conversion catalysts for selective hydrogenation of unsatured compounds, catalysts for three-way automobile exhaust systems, abrasives for chemical polishing slurries, gates for metal-oxide semiconductor devices, and luminescent materials for violet/blue fluorescence [12–14]. Now, the rare earth doped CeO2 (RE2O3–CeO2) have also been considered to be new materials for TBCs and solid oxide fuel cells due to the excellent electrical, mechanical, and thermophysical properties [15–17]. For example, Cao et al. [18] studied the thermal conductivity and thermal expansion coefficient of La2Ce2O7. Patwe et al. [19] reported the lattice thermal expansion of Gd2CexZr2xO7. Zhang et al. investigated the thermophysical properties of (Sm1xGdx)2Ce2O7 [20] and (Sm1xDyx)2Ce2O7 [21]. Zha et al. [22] found that the electrical conductivities of Ce1xGdxO2x/2 (GDC) and Ce1xSmxO2x/2 (SDC) at 700 ℃ are almost equal to the value of YSZ at 1000 ℃. Compared with pure doped ceria oxide (DCO) electrolyte, the DCO–chloride or DCO–carbonate composite electrolyte not only has much higher ionic conductivity, but also shows higher ionic transference number at intermediate temperature range [23,24], and these electrolytes also have good chemical stability [25]. Although thermophysical properties of a few rare earth stabilized CeO2 have been reported by some researchers, the present reports about rare earth stabilized CeO2 applications for TBCs are still not systemic. Therefore, investigation of the thermophysical properties of rare earth stabilized CeO2 is still of notable significance. Previous works have discussed the electrical conductivity of Ce1xSmxO2x/2 system, but did not deal with thermophysical properties of Ce1xSmxO2x/2 oxides. In the present study, Ce1xSmxO2x/2 oxides were synthesized by sol–gel method and pressureless sintering technology (...truncated)


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Xiao-ge Chen, Haoming Zhang, Hong-song Zhang, Yong-de Zhao, Gang Li. Ce1−x Sm x O2−x/2—A novel type of ceramic material for thermal barrier coatings, Journal of Advanced Ceramics, 2016, pp. 244-252, Volume 5, Issue 3, DOI: 10.1007/s40145-016-0196-y