Alan Devoe, a doctoral candidate in materials science and engineering, will defend their dissertation titled “Ceramic Dielectrics for High Temperature Capacitor Applications.” Their advisor, is Fatih Dogan, is professor in the materials science and engineering department. The dissertation abstract is provided below.

Technical progress in microelectronics is allowing operation in environments that were previously considered impossible. Building complete electronic circuits for applications above 450C, such as the planned NASA missions to Venus, require a variety of active and passive components, including multilayer ceramic capacitors (MLCC).

This study explores calcium zirconate CaZrO3 and magnesium oxide MgO based dielectric compositions for MLCC applications that are capable of operating at extreme temperatures between 450C and 600C. Both materials were characterized with respect to impurities, dopants, crystal structure and microstructural development. Dielectric properties were measured to determine permittivity, dissipation factor, and conductivity as a function of temperature, applied voltage and frequency. The MLCC were tested to failure at various voltage and temperature conditions to determine the mean-time-to-failure (MTTF) using Weibull statistics. Calculations were made to estimate lifespan of capacitors under various conditions, including the maximum allowed voltage to achieve a 10-year lifespan at various temperatures.

MgO showed lower conductivity and longer lifespan at all combinations of temperature and voltage but also exhibited lower dielectric constant. Observations indicated that when operating conditions are more demanding, MgO is a superior dielectric. However, when operating at relatively lower temperatures and voltage conditions where both materials can have acceptable lifespan and conductivity, CaZrO3 is superior due to its higher dielectric constant.