Calcium fluoride-based ceramic composites for fuel cell applications

Fuel cells (FC) constructed using CaF₂-based materials as composites were studied. Only H⁺ or O^2- are non-blocking mobile ionic charge carriers, provided by the reversible electrodes from the external gas resources, which contribute the steady-stable FC current output. Conductivity of the CaF₂-based electrolyte materials was obtained from measurements of the FC current-voltage characteristics after subtraction of the electrodes' influence. Although the ac impedance analyses are normally used to determine the conductivity, they may not distinguish the conductivity contributions from specific mobile species because in the fluorides, all mobile charge species can make contributions to the ac conductivity.