Redox characteristics variations in the cation-ordered perovskite oxides BaLnMn₂O_5+δ(Ln = Y, Gd, Nd, and La) and Ca₂Al_1−xGa_xMnO_5+δ(0 ≤ x ≤ 1)

Abstract

Two series of manganese-based oxygen storage materials, BaLnMn 2 O 5+δ (Ln = Y, Gd, Nd, and La) and Ca 2 Al 1-x Ga x MnO 5+δ (0 ≤ x ≤ 1), were synthesized and characterized to clarify cationic substitution effects on the oxygen intake/release behaviors of these materials. The thermogravimetric data revealed that the isovalent substitutions neighboring the active sites for oxygen intake/release are very effective. For BaLnMn 2 O 5+δ , fully-reduced δ ≈ 0 products with larger Ln ions showed oxygen intake starting at lower temperatures in flowing O 2 gas, resulting in a systematic relation between the onset temperature and ionic radius of Ln 3+ . Furthermore, the δ vs P(O 2 ) plots at 700 °C indicated a systematic trend: the larger the ionic size of Ln 3+ is, the larger oxygen contents the Ln-products exhibit. For Ca 2 Al 1-x Ga x MnO 5+δ , on the other hand, the temperature-induced oxygen intake/release characteristics appeared to be influenced by Ga-for-Al substitution, where the onset temperatures of oxygen release (upon heating) and oxygen intake (upon cooling) are decreased with increasing the Ga content (x).

A determination of the oxygen non-stoichiometry of the oxygen storage material YBaMn2O5+

“…The oxygen uptake/release kinetics of YBaMn 2 O 5 þ δ have been studied by Motohashi et al, who also determined the pO 2 dependence of the inter-conversion of YBaMn 2 O 5.5 and YBaMn 2 O $ 6 by thermogravimetric analysis in the pO 2 range 10-10 5 Pa (10 À 4 to 1 atm) and also the range of composition of 'O 6 ' [22][23][24]. We note also that systems with Y partially or completely substituted with other rare-earth elements (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) have been investigated [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44].…”

Solution combustion synthesis of Brownmillerite-type Ca2AlMnO5 as an oxygen storage material

“…This result indicates that Ca 2 AlMnO 5 has the potential to store/release 3.3 wt% of oxygen, which is greater than that of other perovskite-structured materials. In addition, it has been reported that it is possible to change oxygen storage/release performance by changing A-site or B-site components [1].…”

“…Because oxygen is the element most widely used in a variety of chemical reactions [1], large amounts of high purity oxygen are required for various industries. Cryogenic distillation, which exploits the difference in the relative volatilities of oxygen and nitrogen, is the most common air separation process.…”

Oxygen storage capacity and thermal stability of brownmillerite-type Ca2(Al1-xGax)MnO5+δ oxides

“…Recently, Ca2AlMnO5+δ was reported to have a high OSC (~3 wt%) in response to changes in surrounding temperature and pressure of O2 in a highly reversible behaviour, accompanied with the valence change between Mn 3+ and Mn 4+ . [27,[34][35][36] Another similar brownmillerite-type oxide, Ca2GaMnO5 has been investigated about its magnetic structure and oxygen content under different preparation conditions. [37,38] Nevertheless, the detailed understanding on the phase structure and oxygen content in the solid solutions of Ca2(Al1-xGax)MnO5+δ is still not clear.…”