Low‐Temperature Densification of Lanthanum Strontium Manganite (La_1−xSr_xMnO_3+δ), x=0.0–0.20

Abstract

Intermediate‐stage sintering of lanthanum strontium manganite (LSM, where Sr=0.00, 0.05, 0.10, 0.15, and 0.20) was shown in dilatometry studies to be accelerated when subjected to alternating flows of air and nitrogen. The extent of rate enhancement decreased with increased Sr content, and decreased with increased temperature, which coincides with diminished oxygen nonstoichiometry. Shrinkage rates were further shown to be sensitive to the difference in oxygen content in the alternating gas flows. Baseline air sintering rates were measured using stepwise isothermal dilatometry, from which kinetic parameters were calculated using the Makipirtti–Meng model. Activation energies for sintering in air were determined to be 255 ± 26, 258 ± 28, 308 ± 32, 373 ± 37, and 417 ± 41 kJ/mol for Sr=0.0, 0.05, 0.10, 0.15, and 0.20, respectively. A diffusion‐based model is proposed that is consistent with trends in accelerated shrinkage versus temperature. Transient cation vacancy gradients, which lead to higher cation mobility, were calculated from established oxygen diffusivities and oxygen nonstoichiometry as a function of temperature and time. A potential application of this approach is the processing of LSM‐based cathode‐side contact pastes in solid oxide fuel cells.

LaCo0.6Ni0.4O3−δ as cathode contact material for intermediate temperature solid oxide fuel cells

“…Cr in the oxide scale will reacts with Sr in the contact material to form resistive SrCrO 4 phase or replaces the B-site element in perovskite structure to form Cr-containing perovskites [14,21,22]. In order to prevent dimension shrinkage of the contact layer during operation and enhance its adhesion to the oxide scale of the interconnect, pre-sintering of the contact layer in a low oxygen partial pressure atmosphere was found to be effective [11,23]. LaCo x Ni 1Àx O 3 (LCN) perovskite was examined previously as the cathode material.…”

“…The contact layer may act as a barrier or trap to the volatile Cr species, alleviating the damage of cathode caused by the Cr-poisoning. However, there are also some possible adverse effects associated with the use of the contact layer, such as its reactions with adjacent components or dimension shrinkage with time at SOFC operating temperature [11,12].…”

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

“…Solid solutions based on lanthanum strontium manganites La 1-x Sr x MnO 3±δ (LSM) are promising materials for oxygen cathodic electrodes [10][11][12][13][14][15][16][17][18][19] and it is well known that its final properties depend on the La/Sr ratio as well as on the oxygen stoichiometry [20,21]. However, the cathode microstructure is also a critical factor in determining the activity and is controlled by several synthesis variables.…”

“…This LSM system has been synthesized by several techniques [11][12][13][14][15][16][17][18][19][20][21][22][23]; however there are very few works [24][25][26][27][28][29] The aim of this study is to synthesize by a very simple method (one hour using a planetary ball milling equipment at room temperature) eight phases belonging to the system La 1-x Sr x MnO 3±δ (x=0, 0.25, 0.5, 0.75, 0.80, 085, 0.90, and 1) and analyze the structure before and after annealing at 1100º C in static air. The evaluation of how the x value affects the final structure and symmetry, and how far-in terms of the x value-the solid solution is kept were considered.…”

Hydrothermal synthesis of perovskite strontium doped lanthanum chromite fine powders and its sintering

“…This factor can be affected by the thermal stability of the doped lanthanum chromite material, because the chromium evaporation is difficult to avoid during the sintering stage [23]. This was reported to occur on the powders prepared by Pechini's method with similar compositional amount of doping to those used in the present work [10,12].…”