Structure, electrical, and thermal expansion properties of (La_0.8Ca_0.2)(Cr_0.9–xCo_0.1Ni_x)O_3–δinterconnect materials for intermediate temperature solid oxide fuel cells

Abstract

The microstructure, lattice parameters, electrical conductivity, thermal expansion, and mechanical properties of (La 0.8 Ca 0.2 )(Cr 0.9-x Co 0.1 Ni x )O 3-d (x = 0.03, 0.06, 0.09, 0.12) were systematically investigated in this work. Nickel doping of (La 0.8 Ca 0.2 )(Cr 0.9 Co 0.1 ) O 3-d is an effective way of increasing the thermal expansion coefficient (TEC) and stabilizing the high-temperature phase transformation from rhombohedral to tetragonal. As the nickel-doped content increases, the TEC increases parabolically by TEC (x) (ppm/ C) = 10.575 + 63.3xÀ240x 2 (x = 0.03À0.12). The electrical conductivity of (La 0.8 Ca 0.2 )(Cr 0.9-x Co 0.1 Ni x )O 3-d specimens increases systematically with increasing nickel substitution in the range of 0.03 x 0.09 and reaches a maximum for the composition of (La 0.8 Ca 0.2 )(Cr 0.81 Co 0.1 Ni 0.09 )O 3-d (s 850 C $60.36 S/cm). There is a slight increase in the fracture toughness with increasing nickel doping content, and the fracture toughness is strongly affected by the grain size. It seems that there is an increase in the fracture toughness with decreasing grain size. However, the microhardness does not significantly depend on the grain size in this study. The (La 0.8 Ca 0.2 )(Cr 0.81 Co 0.1 Ni 0.09 )O 3-d specimen shows high electrical conductivity, a moderate thermal expansion coefficient, and nearly linear thermal expansion behavior from room temperature to 800 C. It will be suitable for interconnect materials for intermediate temperature solid oxide fuel cells (IT-SOFCs).

Influence of Cr deficiency on sintering, thermal expansion and electrical properties of La0.75Sr0.25Cr1−xO3−δ as a SOFC interconnect material

“…8 Heavy Ca-doping reduces the chemical and dimensional stability in reducing environments. 9 Therefore, an alternative interconnect material is required to overcome the technical limitations of acceptor-doped LaCrO 3 .…”