Dielectrics and capacitors at cryogenic temperature revealed by synchrotron cryo-X-ray microtomography

The functionality/reliability of electronic devices in extreme low temperatures are limited. Therefore, understanding their characteristics at low temperature is important for optimizing the performance/design of individual electronic components. Capacitors are one such electronic components sensitive to temperature. Conventional low temperature electrical characterization lack spatial information. Here we combine synchrotron-cryo-microtomography, finite element modeling, and electrical characterization, to correlate the electrical and microstructural properties within capacitors down to -197 °C. Our experiments reveal that a change in capacitance at low temperature is due to micro-structural changes in the dielectrics, seen as change in cracks opening/closing. We find that the macroscopic/microscopic structural changes are induced by local thermal contraction, and these are stronger with multiple interfacing materials, affecting their electrical characteristics. Our results show new insights towards the functionality of commercial capacitors at low temperatures and provide an important benchmark for developing and designing future capacitors for extreme environmental conditions. • We have demonstrated a novel method to characterize materials at a 77 K environment. • We were able to address the microscopic origin of the change in capacitance in commercial Ta 2 O 5 and ferroelectric multilayer ceramic capacitors at low temperatures, which was previously addressed only by using electrical characterization with no spatial resolution. • A decrease in capacitance at low temperature is typically attributed to a change in permittivity due to structural phase changes. However, from our work we find that the microstructural changes and the induced strain due to the thermal properties of different materials can play a dominant role in the change in capacitance. Potentially altering the permittivity and/or the capacitor geometry.