Enhancing Effect on Densification and Thermal Expansion Compatibility for La[sub 0.8]Sr[sub 0.2]Cr[sub 0.9]Ti[sub 0.1]O[sub 3]-Based SOFC Interconnect with B-Site Doping

Abstract

The air-sintering characteristics and thermal expansion behaviors in the La 1Ϫx Sr x Cr 0.9 Ti 0.1Ϫy Co y O 3 ͑0.15 р x р 0.20 and 0 р y р 0.02͒ and La 0.8 Sr 0.2 Cr 1Ϫx Ti 0.1 M x O 3 ͑M ϭ V and Ni; 0 р x р 0.05͒ systems have been investigated as an interconnect material in high-temperature solid oxide fuel cells ͑SOFCs͒. With the exception of La 0.8 Sr 0.2 Cr 0.85 Ti 0.1 V 0.05 O 3 , all samples showed a single perovskite phase with the hexagonal symmetry. La 0.8 Sr 0.2 Cr 0.85 Ti 0.1 V 0.05 O 3 contained a very small amount of Sr 3 (VO 4 ) 2 . The V, Co, and Ni doping in the La 0.8 Sr 0.2 Cr 0.9 Ti 0.1 O 3 -based perovskite enhanced their air-sintering characteristics, and in particular, the V-doped samples with a V content of 0.02 р x р 0.05 reached у90% relative density after treatment at 1600°C for 20 h. It was found that the V doping in the perovskites had a tendency to decrease an isothermal expansion under a H 2 atmosphere. Thus, La 0.8 Sr 0.2 Cr 0.9x Ti 0.1 V x O 3 perovskites (0.02 р x р 0.05) is a promising candidate for interconnect in high-temperature solid oxide fuel cells.High-temperature solid oxide fuel cells ͑SOFCs͒ with Y 2 O 3 stabilized ZrO 2 ͑YSZ͒ electrolyte are electrochemical and ceramic devices that convert the energy of a fuel directly into electricity without the need for an intermediate combustion stage. Because of their highly efficient and clean conversion of energy, the SOFC system can be applied to a wide variety of electric power generation systems ranging from small cogeneration systems to large power plants. Of all cell configurations, planar cell design is high in power density per volume ͑W/cm 3 ͒, short in electric conductivity paths, and low in production cost. 1 However, there is a serious problem for two kinds of thermal stresses in the planar-type SOFC. Since this cell configuration tends to produce a large temperature difference in the plane direction, the significant problem for enlarging single cell area is imposed by its thermal stresses. Another thermal stress is caused by the mismatch of thermal expansion coefficients among cell components, when the SOFC generator undergoes many thermal cycles between the operating temperature of approximately 1000°C and room temperature. The thermal expansion behaviors of the cell components can be controlled by their chemical compositions. 2 Alkaline earth metal ͑AE͒-doped lanthanum chromite perovskites are widely recognized as interconnect materials in SOFCs. 3,4 However, thermal expansion problems inherent in the LaCrO 3 -based interconnects are known as follows: ͑i͒ nonlinear thermal expansion behavior related to a phase transformation between orthorhombic and rhombohedral symmetries, 5,6 ͑ii͒ large isothermal expansion under reducing atmospheres caused by an oxygen vacancy formation, 7,8 and ͑iii͒ average linear thermal expansion coefficient ͑TEC͒ mismatch between the LaCrO 3 -based interconnect and the other cell components. 9,10 To solve the TEC mismatch problems, many studies have been conducted using the technique of B-s...

Current status and perspectives of rare earth catalytic materials and catalysis

“…Interconnecting materials are mainly alloys (Ni-Cr) with high temperature resistance and doped perovskite-type composite oxides (La1-xCaxCrO3 or La0.8Sr0.2Cr0.9Ti0.1O3) [130,131]. To avoid the shortcomings of composite oxides, i.e.…”

25 Conducting solids

“…Similarly, small levels of V, Co, Ni doping were shown to enhance the air sintering characteristics of La 0.8 Sr 0.2 Cr 0.9 Ti 0.1 O 3 , with V doping giving the greatest effect. 142 Ovenstone et al have shown that a combination of hydrothermal processing followed by high temperature sintering resulted in dense pellets of La 0.7 Ca 0.3 CrO 3 and La 0.84 -Sr 0.16 CrO 3 at lower temperatures than by conventional synthesis routes. 143 Further work on supported mixed gas SOFCs was presented by Raz et al 144 In these systems the anode and cathode are both exposed to the same mixture of gases, and the potential is generated due to the differences in catalytic activities between anode and cathode.…”

Characteristics of La_0.8Sr_0.05Ca_0.15CrO₃ Interconnect Material for SOFC Synthesized by a Modified Pechini Method, USP, and GNP

“…The substitution of either on A or B sites in the ABO3 perovskite materials is currently used to improve electrical properties and sintering behavior. Although thermal-electrical properties of the alkaline-earth-doped lanthanum chromites is good, its sintering behavior is very bad in air due to the high vapor pressure of the chromium oxide [1][2][3][4][5]. Therefore, several attempts to overcome this bad weak point have been performed to densify lanthanum chromites and to improve the sintering behavior [6][7][8][9][10][11][12][13].…”