Development of a voltage‐applicable heating specimen holder for in situ observations of solid oxide fuel cells with an environmental transmission electron microscope

A voltage‐applicable heating specimen holder is developed to observe solid oxide fuel cells (SOFCs) in an environmental transmission electron microscope. An SOFC specimen can be heated and has a voltage applied in an oxygen gas atmosphere using the holder. Oxygen ion migration and redox reactions in the specimen could also be realized. The heating unit, which consists of nickel–chromium alloy mounted on the tip of the developed specimen holder, can heat the specimen up to 1200 K in an oxygen gas atmosphere. A specimen preparation method for the SOFC structure is also established using a focused ion beam technique. The holder has high stability for high‐resolution imaging and electron energy loss spectroscopy under the in situ condition. The mechanical and electrical stabilities are estimated from high‐resolution images and electron energy loss spectra of the heated and voltage‐applied specimen in an oxygen gas atmosphere. The developed holder is a powerful tool to reveal the microstructural and electronic structural changes that occur by electrochemical reactions at the interfaces of an SOFC.