Enhancement of grain growth and electrical conductivity of La0.8Sr0.2MnO3 ceramics by microwave irradiation

We studied crystallization, grain growth and electric properties of La_0.8Sr_0.2MnO₃ (LSM) ceramics which were produced using the microwave-treatment. While co-precipitated nanoparticles remain mainly amorphous, the microwave irradiated particles are crystallized into LSM and La₂Mn₂O₇ at 550 °C, due to higher dielectric polarizability of La. This, in turn, decreases the amount of the second phase La₂O₃ in calcined powder and promotes the growth of perovskite grains during sintering at 1400 °C. Larger grains of LSM ceramics lower the activation energy of small polaron hopping from 0.35 eV to 0.24 eV and increases high-temperature electric conductivity. In addition, high crystallinity of LSM ceramics from the microwave-treatment suppresses a chemical reaction with ZrO₂ and NiO in a temperature range of 900 – 1100 °C under oxidizing and reducing ambiances. These results show that LSM ceramics from the microwave-assisted reaction meet requirements for an interconnect layer for solid oxide electrolysis cells.