Using scanning spreading resistance microscopy, we obtained images of local conduction paths on the cross section of a multilayer ceramic capacitor (MLCC) just before electrical breakdown. The images were observed after the local low-resistance part in the MLCC was identified as being degraded according to the highly accelerated lifetime test. Each grain in the conductive path images was clearly visible, and the insulation resistance (IR) around the cathode was lower than that near the anode. It was concluded that this is a phenomenon that accompanies the migration of oxygen vacancies. We directly observed the degraded resistance distribution of ceramic grains, which showed the bulk-limited conduction mechanism formed by IR degradation.

A self-powered system with a long lifetime would represent an opportunity in the development of a next-generation, standalone Internet of Things. Ceramic capacitors are promising candidates for energy storage components because of their stability and fast charge/discharge capabilities. However, even the energy density of state-of-the-art capacitors needs to be increased markedly for this application. Improving the breakdown electric field represents a potential solution, but operations at such high fields relying on unchanged dielectric permittivity sacrifice the lifetime of the capacitor to some degree. Here, we report ferrorestorable polarization engineering capable of more than doubling the effective permittivity. Our experiments and ab initio calculations demonstrate that a defect dipole composed of Cu3+ and oxygen vacancy in a prototypical ferroelectric BaTiO3 ceramic is coupled with spontaneous polarization. The resultant ferrorestorable polarization delivers an extraordinarily large effective relative permittivity, beyond 7000, with a high energy efficiency up to 89%. Our work paves the way to realizing efficient ceramic capacitors for self-powered applications.

The temperature distribution around a degraded area of an exfoliated multilayer ceramic capacitor (MLCC), just before electrical breakdown (pre-breakdown) was measured. The temperature increase of the heating spot was in good agreement with the temperature evaluated from Joule heating by the applied voltages and the current. The current–voltage characteristics and the temperature dependence on the insulation resistance of the exfoliated sample showed the same characteristics as unexfoliated samples. We have confirmed that the locally degraded areas dominate the electrical properties of pre-breakdown MLCCs.

No abstract

A self-powered system with a long lifetime offers an opportunity to develop a next-generation, standalone Internet of Things. Ceramic capacitors are promising candidates for energy storage components because of their stability and fast charge/discharge capability. Even for state-of-the-art capacitors, the energy density needs to be increased markedly. Improving breakdown electric fields provides a potential solution, but operations at such high fields relying on unchanged dielectric permittivity sacrifice the lifetime to some degree. Here, we report a ferrorestorable polarization engineering capable of enhancing effective permittivity over twice. Our experiments and ab initio calculations demonstrate that a defect dipole composed of Cu3+ and oxygen vacancy in a prototypical ferroelectric BaTiO3 ceramic is coupled with spontaneous polarization. The resultant ferrorestorable polarization delivers an extraordinarily large effective relative permittivity beyond 7,000 with a high energy efficiency up to 89%. Our work paves the way to realizing efficient ceramic capacitors for self-powered applications.