An anomalous low dose phenomenon in gamma irradiated BaTiO3-based commercial multilayer ceramic capacitors

Owing to its miniaturization and high dielectric permittivity, BaTiO3-based multilayer ceramic capacitors (MLCCs) have attracted more and more attention in recent years, and are widely used in gamma-ray environments, such as nuclear and space application. Compared to the extensively studied thermal or electrical reliability issues, the potential risks caused by irradiation have not been well understood, let alone the dielectric structure changes. Unlike the common monotonic dose-dependent trend, we found non-monotonic results in MLCCs with low dose, named as the anomalous low dose (ALD) phenomenon. That is the capacitance decreases at low gamma-ray doses, and then abnormally recovers to the initial value at high doses. Similar cases have been found in almost all the physical properties of MLCCs. Intensive characterizations help to confirm that it is the dose-dependent consistent lattice and electronic structure changes that are most likely to cause this anomalous phenomenon. In detail, the gamma irradiation induces charged defects and consequently lattice distortion, which reduces the number of domains with low-field inversion and eventually causes the capacitance decrease. This work provides a new cognition about the gamma irradiation effect of BaTiO3-based (BTO) dielectrics and commercial MLCCs based on BTO.