GDC (typically Ce0.9Gd0.1O1.95 or Ce0.8Gd0.2O1.9) is favored over Yttria-stabilized Zirconia (YSZ) for operations between 500°C and 700°C due to its significantly higher ionic conductivity.

In electrolyte-supported cells, the GDC pellet acts as the structural backbone (usually 150–500 um thick). The advantage is high oxygen ion (O2-) conductivity allows for lower ohmic resistance at reduced temperatures. While its challenge is In reducing atmospheres (anode side), Ce^{4+} can reduce to Ce^{3+}, introducing electronic conductivity. This creates an internal short circuit, lowering the Open Circuit Voltage (OCV).

GDC pellets are frequently used as substrates to test the Area Specific Resistance (ASR) of new electrode materials (e.g., LSCF or SSC). By screen-printing the same electrode on both sides of a dense GDC pellet, you can use Electrochemical Impedance Spectroscopy (EIS) to isolate electrode performance without the complexity of a full fuel cell.

References:

1. S. J. Kim, et al.,Effect of Ce0.43Zr0.43Gd0.1Y0.04O2−δ contact layer on stability of interface between GDC interlayer and YSZ electrolyte in solid oxide electrolysis cell, J. Power Source, 2015, 284, 617-622.
2. H. Fan, et al., Electrochemical performance and stability of lanthanum strontium cobalt ferrite oxygen electrode with gadolinia doped ceria barrier layer for reversible solid oxide fuel cell, J. Power Sources, 2014, 268, 634-639.