Structural characterization and electrochemical properties of (La,Sr)(Al,Mg)O_4−δ perovskites

Abstract

LaSrAl1−xMgxO4−δ (x = 0.0–0.3) layered perovskites were synthesized by a nitrate–citrate route followed by annealing in air at 1100 °C, and studied as potential electrolyte materials in solid oxide fuel cells (SOFCs).

Structural and Electrical Characterization of LaSrAl1−xMgxO4−δ Layered Perovskites Obtained by Mechanical Synthesis

“…The backscattered electron image shows that Mg-doped LaSrAlO 4 has minimal segregation in the dark gray regions where there is a higher Sr content at an La/Sr = 0.95 ratio. The light gray area shows an La/Sr = 1.16 ratio, which does not generate a great impact on Mg segregation, as seen in previous work with chemical synthesis [12]. The black region corresponds to the pores and a densification of 85% was calculated by the imaging method.…”

“…The main diffraction planes (103) and (110) are observed in the inset of Figure 3a. The plot in Figure 3b shows the results of the unit-cell volumes and crystallite size (coherent diffraction pattern) of the Mg series obtained by SM mechanical synthesis (this work) and CN citrate-nitrate chemical synthesis (previous work) [12], both annealed at 1100 • C. It is seen that the unit-cell volume is slightly larger by SM, which may reveal a better tendency to incorporate Mg at the 2a (1/2 1/2 1/2) site of Al. The crystallite size for the SM is also lower than that of the crystallites obtained by CN synthesis.…”

“…There are alternative crystalline structures such as K 2 NiF 4 -type layered perovskites, which have attracted the attention of researchers for their non-stoichiometric capabilities, enabling the incorporation of anionic vacancies and/or interstitial oxygen atoms, which greatly improve their electrical properties [11]. In previous works, we synthesized K 2 NiF 4 -type perovskites with LaSrAl 1−x Mg x O 4−δ [12] and LaSrGa 1−x Mg x O 4−δ [13] compositions, where the incorporation of divalent Mg to the parent LaSrAlO 4 or LaSrGaO 4 oxides improved the conductivity by three orders of magnitude. Crystallographic studies by neutron diffraction allowed us to characterize the oxygen diffusional pathways, showing that the open structure favors the movement of the oxygen ions across the crystal through the interstitial sites of the structure, thus obtaining conductivities up to 3 mS/cm at 900 • C [12,13].…”

“…In previous works, we synthesized K 2 NiF 4 -type perovskites with LaSrAl 1−x Mg x O 4−δ [12] and LaSrGa 1−x Mg x O 4−δ [13] compositions, where the incorporation of divalent Mg to the parent LaSrAlO 4 or LaSrGaO 4 oxides improved the conductivity by three orders of magnitude. Crystallographic studies by neutron diffraction allowed us to characterize the oxygen diffusional pathways, showing that the open structure favors the movement of the oxygen ions across the crystal through the interstitial sites of the structure, thus obtaining conductivities up to 3 mS/cm at 900 • C [12,13].…”

“…The onset is a graphic representatio principal planes (103) and (110). (b) Crystallite size and unit-cell volume obtained by mec synthesis and chemical synthesis (previous work[12]). (c) Visualization of the unit cell of the perovskite (K2NiF4 type) of LaSrAl0.7Mg0.3O4 − −δ (x = 0.1-0.3) and its respective coordination dra.…”