P-Type electronic conduction in CeO2- and LaGaO3-based solid electrolytes

Abstract

Abstract.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 ptype conductivity of compositions based on La(Sr)Ga(Mg)O3_s (LSGM) and Ce(Gd)O2.s (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 Ce0.80Gd0.2002.s 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 ptype electronic conductivities of LaGaO3-based phases are higher than those in CGO. The electronhole 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.

Oxygen Nonstoichiometry, Conductivity, and Seebeck Coefficient of La0.3Sr0.7Fe1−xGaxO2.65+δ Perovskites

“…Therefore, the structure of the title materials in air was refined as cubic without deterioration of the refinement quality. This conclusion was confirmed by the neutron powder diffraction data at room temperature (26 , and/ or a greater level of structural disorder when gallium is introduced in the lattice. The ionic radius of Ga 3+ is smaller than that of high-spin Fe 3+ in the same coordination (27).…”

Influence of Point‐Defect Reaction Kinetics on the Lattice Parameter of Ce0.8Gd0.2O1.9

“…Upon first heating (annealing), the asdeposited films do not expand although they were kept successively at 100 (6 h), 350 (4 h), and 530 8C (2 h). It must be pointed out that, at 530 8C, the difference in the thermal expansion coefficients of the Si substrate and Ce 0.8 Gd 0.2 O 1.9 should have resulted in a compressive strain of: [20] DaDT ¼ ð11:5 À 3:1Þ Â 10 À6 ½K À1 Á 500 ½K ¼ 0:42% (2) where Da ¼ (11.5-3.1) Â 10 À6 K À1 Á is the average difference between the thermal expansion coefficients of Ce 0.8 Gd 0.2 O 1. 9 and Si (see Sec.…”

“…5.5), which matches the value obtained for rapidly heated selfsupported Ce 0.8 Gd 0.2 O 1.9 films [5] and is close to the value reported in the literature for bulk Ce 0.8 Gd 0.2 O 1.9 (11.5 Â 10 À6 K À1 ). [20] This also agrees with data that indicates that no oxygen loss takes place in Ce 0.8 Gd 0.2 O 1.9 below 700 8C. [7] However, after the annealed films had been kept for over four months at room temperature, their out-of-plane lattice parameter spontaneously expanded by 0.78% (the d spacing of the (220) reflection increased from 1.925 to 1.940 (AE0.002) Å ) (Figs.…”

“…This value differs by only 10% from that measured for the bulk Ce 0.8 Gd 0.2 O 1.9 (i.e., 11.5 Â 10 À6 K À1 ). [20] Within the course of a few months at room temperature, the out-ofplane lattice parameter increases spontaneously. However, after subsequent heating above 250 8C, the films again exhibit a thermal expansion coefficient of 10.5 Â 10 À6 K À1 .…”

Synthesis, Structural and Physicochemical Characterization of BaFe1-xAlxO3−δ Oxides

“…A few years ago, several studies have shown that the isovalent doping into the Fe sublattice with trivalent cations having stable oxidation state, such as Ga or Al, enhance the stability of perovskite ferrite [16][17][18]. On the other hand, another work on Al-doped perovskite anodes for oxidation of hydrogen in IT-SOFC has been carried out [18].…”