LA-ICP-MS and EDS characterization of electrode/electrolyte interfaces in IT-SOFC materials

Abstract

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in combination with scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) is used for the determination of elemental spatial distribution in ceramic multi-layer systems such as those found in intermediate-temperature solid oxide fuel cells (IT-SOFCs). Because layer sintering occurs at high temperature (usually well over 1000 °C), there may be mutual diffusion of ions from one layer to another, with dramatic consequences on cell performances. In this work, two model materials have been used to test LA-ICP-MS: La_0.83Sr_0.17Ga_0.83Mg_0.17O_2.83 (LSGM), one of the most promising electrolytes for IT-SOFCs, and La_0.8Sr_0.2MnO₃ (LSM), a highly representative perovskite material, which are amply used to design electrode materials. A two-layer system screen printed onto an LSM pellet (LSM–LSGM–LSM pellet) was successively sintered at a typical processing temperature, i.e. 1300 °C, for a short time (1 h). Elemental spatial distribution was determined by line profile analyses carried out on fracture surfaces; for comparison SEM-EDS line profiles were tested on the same surface. LA-ICP-MS line profile analysis evidenced that, notwithstanding the relatively low sintering temperature and short firing time (1 h per sintering), manganese cation diffusion into LSGM is relatively abundant, in agreement with previous literature reports and present EDS results. While line scan EDS analyses are not as conclusive for Ga and Mg diffusion, LA-ICP-MS shows that both ions diffuse across both interfaces, and Ga diffuses even over very long distances into the LSM pellet; on the contrary, only trace amounts of Mg can be found far from the LSGM/LSM interface.