One of the biggest challenges for in situ heating transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) is the ability to measure the local temperature of the specimen accurately. Despite technological improvements in the construction of TEM/STEM heating holders, the problem of being able to measure the real sample temperature is still the subject of considerable discussion. In this study, we review the present literature on methodologies for temperature calibration. We analyze calibration methods that require the use of a thermometric material in addition to the specimen under study, as well as methods that can be performed directly on the specimen of interest without the need for a previous calibration. Finally, an overview of the most important characteristics of all the treated techniques, including temperature ranges and uncertainties, is provided in order to provide an accessory database to consult before an in situ TEM/STEM temperature calibration experiment.

Oxidation states of cations in a perovskite structure play an important role for conductivity in solid oxide electrochemical cells. For bulk materials oxidation states can be calculated for specific conditions, but is not well understood for micro− /nanostructured materials and at interfaces between materials. We present a fundamental study of interfaces between La 0.6 Sr 0.4 CoO 3-δ (LSC) and yttria-stabilized zirconia (YSZ) in symmetric model solid oxide electrochemical cells. Nanoscale morphology as well as the chemical state of the LSC are investigated by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The experiments were performed in situ at temperatures up to 600 • C in high vacuum (ca. 10 − 7 mbar) and in 2 mbar oxygen. The measured LSC Co oxidation at room temperature is lower than that expected for bulk LSC, indicating a high oxygen vacancy density and possibly high ionic conductivity. However, the Co oxidation state increases with increasing temperature, both in oxygen and in vacuum. The results shows that the Co oxidation state approach that expected for bulk LSC for typical solid oxide fuel or electrolysis cell operation temperatures.