Electrical conduction behaviors and mechanical properties of Cu doping on B-site of (La_(0.8)Ca_(0.2))(Cr_(0.9)Co_(0.1))O_(3-δ) interconnect materials for SOFCs

摘要

The microstructure, lattice parameters, mechanical properties, and electrical conductivity mechanisms for Cu doping on B-site of (La_(0.8)Ca_(0.2))(Cr_(0.9)Co_(0.1))O_3-δ have been systematically investigated. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of hole with the electrical conductivity. The information of charge compensation mechanisms and defect formation may be valuable for a better understanding of the interconnect of (La_(0.8)Ca_(0.2))CrO_3-δ abased ceramics used for solid oxide fuel cells (SOFCs). The electrical conductivity increases with the increase in temperature in air, whereas the electrical conductivity has a maximum value at a certain temperature in 5% H_2-95% Ar. The concentration of hole at high oxygen activity is larger than that at low oxygen activity. Because (La_(0.8)Ca_(0.2))CrO_3-δ abased ceramics are p-type conductors, the electrical conductivity is dominated by the concentration of hole. Obviously, the electrical conductivities of Cu doping on B-site of (La_(0.8)Ca_(0.2))(Cr_(0.9)Co_(0.1)CrO_3-δ in air are larger than those in 5% H_2-95%. At higher Cu-doping levels, higher temperatures, and high oxygen activity, the compensation mechanism is significantly dominated by the formation of oxygen vacancy, i.e. ionic compensation. On the contrary, the compensation mechanism is significantly dominated by the formation of the formation of Cr~4+, i.e. electrical compensation at lower Cu-doping levels, higher temperatures, and lower oxygen activity. Because mechanical properties of SOFCs interconnect materials are very important in reducing~(-1)tmosphere, the effect of atmospheres on fracture toughness and microhardness for specimens is investigated, which results revealed that when specimens were exposed to 5% H_2-95% Ar forming gas, all specimens appeared to have hydrogen-induced cracking (HIC) except for (La_(0.8)Ca_(0.2))(Cr_(0.9)Co_(0.1))CrO_3-δ . Although the exact mechanism of HIC is still not clear, it is known from this study that Cu doped in the B-site of (La_(0.8)Ca_(0.2))(Cr_(0.9)Co_(0.1))CrO_3-δ enhanced HIC damage and with the increase of Cu-doping level, the degree in HIC is increased.