P-Type Electronic Conduction in CeO2- and LaGaO3-Based Solid Electrolytes

Modifications of the e.m.f, and faradaic efficiency techniques, taking into account electrode polarization in the measuring cells, in combination with the use of electrodes having sufficiently high polarization resistances enable a precise determination of minor electronic contributions to the conductivity of solid electrolytes. These methods were used to determine the p-type conductivity of compositions based on La(Sr)Ga(Mg)O3-delta(LSGM) and Ce(Gd)O2-delta (CGO) at 900-1270 K. The oxygen ion transference numbers of these materials under oxygen/air gradient vary in the range 0.999-0.970, increasing with decreasing temperature. Substitution of 2 % gadolinium in Ce0.80Gd0.2O2-delta with praseodymium was found to increase the electron-hole conduction by 2.5 - 4 times. At temperatures above 700 K, both the partial oxygen ionic and p-type electronic conductivities of LaGaO3-based phases are higher than those in CGO. The electron-hole transport in LSGM tends to increase with the magnesium concentration, while the activation energy is essentially independent of composition. Electronic conduction in CGO and LSGM electrolytes was also found to be influenced by the ceramic microstructure.