Calcium doped lanthanum chromite conductivity

Sakai N, Kawada T, Yokokawa H, Dokiya M, and Iwata T. Sinterability and electrical conductivity of calcium-doped lanthanum chromites. J. Mater. Sci. 1990 25-,4531-4534. 

Yasuda I and Hikita T. Electrical conductivity and defect structure of calcium-doped lanthanum chromites. 7. Electrochem. Soc. 1993 140 1699-1704. 

I. Yasuda and T.J. Hikita, Precise determination of the chemical diffusion coefficient of calcium-doped lanthanum chromites by means of electrical conductivity relaxation, Electrochem. Soc., 141(5) (1995) 1268-1273. 

The anode material in SOF(7s is a cermet (rnetal/cerarnic composite material) of 30 to 40 percent nickel in zirconia, and the cathode is lanthanum rnanganite doped with calcium oxide or strontium oxide. Both of these materials are porous and mixed ionic/electronic conductors. The bipolar separator typically is doped lanthanum chromite, but a metal can be used in cells operating below 1073 K (1472°F). The bipolar plate materials are dense and electronically conductive. 

Lanthanum chromite is the most common base for SOFC interconnects, but chromites of other lanthanide elements have also been used [43, 45, 46, 48, 54, 55], Although the conductivity of calcium-doped gadolinium chromite for low calcium contents is in the upper range of conductivities for lanthanum chromite, other nonlanthanum chromites typically have lower conductivities. However, the use of other lanthanides provides benefits in controlling the phase transformation temperature and in potential cost savings [48],... 

Lanthanum chromite is a p-type conductor so divalent ions, which act as electron acceptors on the trivalent (La3+ or Cr3+) sites, are used to increase the conductivity. As discussed above, the most common dopants are calcium and strontium on the lanthanum site. Although there is considerable scatter in the conductivities reported by different researchers due to differences in microstrucure and morpohology, the increase in conductivity with calcium doping is typically higher than that with strontium doping [4], The increase in conductivity at 700°C in air with calcium additions is shown in Figure 4.1 [1, 2, 28-44], One of the advantages of the perovskite structure is that it... 

---