Defect Structure of Mg‐Doped LaCrO₃ Model and Thermogravimetric Measurements

Abstract

Chemical stability and cation stoichiometry determine the applicability of LaCr03 as a high-temperature oxide electrode. A model for the behavior of acceptor-doped LaCrO, as a function of oxygen activity is proposed. The model is in agreement with experimental data on Mg-doped LaCrO,. Stability regimes and compensation mechanisms at various oxygen activities and temperature are presented.

Electrical conduction behaviors of isovalent and acceptor dopants on B site of (La0.8Ca0.2)CrO3−δ perovskites

“…The formation of Cr 4+ belongs to electronic compensation, whereas the formation of oxygen vacancies belongs to ionic compensation. Whether such a substitution favor either electronic or ionic compensation will depend on the conditions which equilibration of LaCrO 3 takes place [19]. For simplicity, it is assumed that p-type disorder predominates in nonstoichiometric LaCrO 3 , and all defects are fully ionized.…”

Oxygen vacancy formation and defect structure of Cu-doped lanthanum chromite LaCrCuAlO

“…We found (see Section 4) that LaCr 0.79 Cu 0.05 Al 0.16 O 3Àd remains slightly understoichiometric with respect to oxygen at 1000 8C in air. This is in contrast to other doped chromite compositions which are practically of stoichiometric composition with respect to oxygen even at lower oxygen partial pressure than that of air [5][6][7][8][9]. This observation gave rise for the development of a second model of the defect structure of LaCr 0.79 Cu 0.05 Al 0.16 O 3Àd which bases on the lack of valence change for the cation Cr 3+ over the complete oxygen partial pressure range investigated.…”

“…The presence of Cu only in the 2+ oxidation state was assumed by Jin et al [4] in order to explain their data on the electrical conductivity of LaCr 1Àx Cu x O 3 . This means that Cu additions in LaCrO 3 act like the acceptor dopant Mg giving rise to the formation of tetravalent chromium as a result of charge compensation [7,8]. The process of oxygen release from the chromite lattice under reducing conditions is then accompanied by the transition of Cr 4+ to Cr 3+ according to the bsmall polaronQ reaction.…”

Measurement of electrical conductivity of La0.2Sr0.8Cr0.2Fe0.8O3-δ using gas-tight electrochemical cells

“…3). For non-interacting and dilute defects, σ is proportional to (pO 2 ) ¼ , assuming constant mobility [38,39]. Since 80% of the A site is occupied with Sr, high oxygen deficiency is observed at elevated T and hence defect interactions and association are expected, leading to lower values of the exponent.…”