PNNL

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 decreases with increased temperature, which coincides with diminished oxygen non-stoichiometry. Shrinkage rates were shown further 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 non-stoichiometry as a function of temperature and time. A potential application of this approach is processing of LSM-based cathode-side contact pastes in solid oxide fuel cells.