Defect Chemistry of (La,Sr)MnO3

Abstract

Defect-disorder models are derived for undoped and strontium-doped LaMnO 3 . A random-defect model and a cluster-defect model are both considered within the regimes that correspond to oxygen deficit and oxygen excess. The models are constructed based on the experimental nonstoichiometry data that was reported by previous researchers. According to both models, the addition of strontium leads to an increase of the concentration of electron holes and oxygen nonstoichiometry. The defect clusters that are predicted by the cluster model have a marked concentration only at very low oxygen partial pressures. Both models are verified against the electrical-conductivity data. A good agreement between the random-defect model and the experimental data is shown.

Thermodynamic and kinetic assessments of strontium-doped lanthanum manganite perovskites for two-step thermochemical water splitting

“…Most commonly, thermodynamic parameters are extracted with the goal of understanding defect chemistry and hence are concerned with the specics of a defect model that can address, for example, possible defect association or clustering. 22,26 While useful for meeting the objective of elaborating defect chemistry, such an analysis ultimately imposes some functional form for the dependence of enthalpy and entropy on d, and discrepancies between the model and measured data can be anticipated to lead to large errors upon extrapolation to temperatures at which measurements were not performed.…”

Ab initiodefect energetics of perovskite (001) surfaces for solid oxide fuel cells: A comparative study ofLaMnO3versusSrTiO3andLee1, Morgan2 2015Phys. Rev. B433360View full textAdd to dashboardCite

“…Point defects, including ionic and electronic defects, play a crucial role in the oxygen reduction reaction activity of perovskite type mixed ionic-electronic conductors, as both ionic/electronic conductivity and oxygen surface exchange are strongly influenced by the content of point defects in perovskite type mixed ionic-electronic conductors [2,[4][5][6]. The dominant charge carriers in LSM (for x 0.5 in LSM) are electron holes in the entire oxygen partial pressure region before decomposition [7,8], while the low oxygen vacancy concentration in bulk LSM leads to poor ionic conductivity under most conditions. The low oxygen vacancy concentration distinguishes LSM from most other cathode materials, which have higher oxygen vacancy concentrations and therefore allow transport oxygen through their bulk during their operation in a solid oxide fuel cell cathode [2].…”

“…It is generally assumed that transport along a surface path plays a critical role in the LSM cathodic reaction rate, although * Corresponding author: ddmorgan@wisc.edu at high over potential the substantially reduced LSM can create a large content of oxygen vacancies and the bulk path will become colimiting [2,9]. Although understanding of the LSM bulk defect chemistry under solid oxide fuel cell conditions (900-1200 K in air) has been improved over the last two decades [8,[10][11][12][13][14][15], surface defect chemistry, which is critical to oxygen reduction reaction performances [4,5], still remains largely unknown. This limited knowledge is due to difficulties in characterizing perovskite surfaces and the sensitivity of the chemistry to processing history and operating conditions.…”

Effect of microstructure on the conductivity of porous (La0.8Sr0.2)0.99MnO3

“…As previously reported, at higher temperature (1273 K) the electrical conductivities hardly varied in the region measured, 11) and the conductivity at 1273 K was 100 S/cm. According to the defect model of Nowotny and Rekas, 12) the equilibrium between defects and oxygen is expressed by the following reaction: (2) In this study, at lower temperatures from 573 K to 873 K, Fig. 5 shows a small PO 2 dependence of the electrical conductivity.…”