Microstructural and electrical properties of Ce 0.9 Gd 0.1 O 1.95 thin-film electrolyte in solid-oxide fuel cells
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Jung-Hyun Kim Electrochemical Energy Laboratory and Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas 78712
Xinghang Zhang Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843-3123
Arumugam Manthiram Electrochemical Energy Laboratory and Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas 78712
Haiyan Wanga) Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas 77843-3128 (Received 10 March 2010; accepted 5 October 2010)
Microstructural and electrical properties of Gd-doped CeO2 (GDC; Ce0.9Gd0.1O1.95) thin films prepared by pulsed laser deposition as an electrolyte in solid-oxide fuel cells (SOFCs) were investigated. The GDC thin films were prepared on various substrates including single-crystal yttriastabilized zirconia (YSZ) and magnesium oxide (MgO) substrates. The GDC thin-film electrolytes with different grain sizes and grain morphologies were prepared by varying the deposition parameters, such as substrate temperature, oxygen partial pressure, target repetition rate, and laser ablation energy. The microstructural properties of these films were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Alternatingcurrent (AC) and direct-current (DC) electrical measurements through in-plane method show that the electrical property of the GDC thin film strongly depends on grain size, e.g., the total conductivity of the films deposited at 700 °C (7.3 10 3 S/cm) is about 20 times higher than the ones deposited at room temperature (3.6 10 4 S/cm) at the measurement temperature of 600 °C.
I. INTRODUCTION
Compared with other fuel cell types, solid-oxide fuel cells (SOFCs) have high-power efficiency and excellent long-term performance stability and are an environmentally friendly alternative to conventional energy-conversion devices.1 Currently, the high internal resistance (IR) loss of electrolyte requires high operating temperature in SOFCs. To tackle this problem, there are several main approaches, including an increase in the ionic conductivity of the electrolyte by searching for new electrolyte materials such as gadolinia-doped ceria (GDC) and La1 xSrxGa1 y MgyO3 d (LSGM),2–7 reducing the thickness of electrolyte,8–10 and decreasing electrode polarization resistance.11,12 Some of the most successful approaches to reduce the operating temperature are to grow thinner electrolyte using thin-film fabrication technique and to select new electrolyte materials with higher ion conductivity.13 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2010.72 854
J. Mater. Res., Vol. 26, No. 7, Apr 14, 2011
http://journals.cambridge.org
Downloaded: 29 Mar 2015
From the materials selection viewpoint, yttria-stabilized zirconia (YSZ) is one of the well-known electrolytes for SOFC applications. To achieve sufficiently high ion conductivity, a high operating temperature, typically around
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