Room temperature mechanosynthesis of the La1−Sr MnO3± (0≤x≤1) system and microstructural study

Abstract

Monophase nanocrystalline powders belonging to the La 1-x Sr x MnO 3±δ system (0≤x≤1) with a perovskite structure have been obtained by mechanochemistry synthesis using a planetary ball milling equipment from La 2 O 3 , SrO, and Mn 2 O 3 mixtures. The solid state reaction was complete after one hour of milling treatment. For all the compositional range, the diffraction domain was very small and the structure appeared as a pseudo cubic perovskite. After annealing at 1100°C under static air, the symmetry evolution due to the La substitution by Sr was analyzed by x-ray and electron diffraction. Samples with x = 0, 0.25, 0.5, and 0.75 were assigned to R-3c space group (167) in the rhombohedral system and perovskite structure. However, the symmetry of the last term of the system (x=1), SrMnO 3±δ sample, changed to P6 3 /mmc space group (194) in the hexagonal system. The terms with x = 0.8, 0.85, and 0.9 presented mainly rhombohedral symmetry.

Chemical and electrical properties of LSM cathodes prepared by mechanosynthesis

“…All of these results are in accordance with our previous work [7], which demonstrates the scalability of mechanosynthesis as it is possible to obtain 6 g instead of 2 g (in 1 h of milling) of LSM material only by incrementing slightly the milling time (see table I). This makes evident some of the advantages of mechanochemistry over other synthetic methods, since the traditional ceramic method requires a temperature of 1000-1200 ºC [13]; or its scalability contrasted with Pechini, citrate [14] or plasmaspraying methods [15][16][17].…”

“…Similar results were found in our previous work [7]; although in that case all milled samples presented the pseudo-cubic symmetry ( Fig. 2 in ref.…”

“…[7]). This difference could be due to the higher milling intensity regime used in [7] (ball-to-powder ratio (BPR) of 92 instead of 31 as in present work), which probably induced a further decreasing of the coherent diffraction domains. After the sintering treatment (Fig.…”

“…A structural study of this system, also prepared by mechanochemistry, was recently published by Sayagués et al. [7], although smaller amounts of samples were synthesized. A summary of the obtained structural results is presented here also to demonstrate the scalability of mechanochemistry.…”

Development by Mechanochemistry of La0.8Sr0.2Ga0.8Mg0.2O2.8 Electrolyte for SOFCs

“…It has been shown in previous studies that mechanochemistry is an appropriate method to synthesize complex solid solutions with a perovskite structure that can be used as an electrolyte [27,28] (LSGM system), cathode [29,30] (LSM system, La 1−x Sr x MnO 3 ), or anode [31] (SLT system, Sr 1−x La x TiO 3 ) in SOFCs. Mechanochemistry is a relatively simple process that uses the mechanical energy provided by ball mills to induce solid-state reactions at room temperature in a wide variety of powder reactant mixtures.…”