High reliable non-reducible ultra-fine BaTiO3-based ceramics fabricated via solid-state method

The ultra-thin multilayer ceramics capacitors (MLCCs) with layer thickness less than 1 μm are in urgent demand due to the rapid development of modern electronic industries. However, the preparation of the dielectric materials with the desirable grain size <150 nm is a huge challenge. In this work, the ultra-fine BaTiO3 (BT) powders (<120 nm) prepared via solid-state reaction method, hydrothermal method and hydrothermal method following a heat treatment (850 °C) are selected to prepare the nano-crystalline non-reducible BT-based ceramics, respectively. The effect of the synthesis methods on the microstructure, electric performance and the reliability of the BT-based ceramics are studied. The results of the Raman, XPS and FT-IR spectroscopy demonstrate that a large number of internal stresses and point defects (hydroxyl/proton defects, Ba vacancies) are existed in the hydrothermal powders and can be eliminated to some extent by a proper heat treatment. Unfortunately, plenty of nano-pores (10–20 nm) are observed in the hydrothermal powders, which cannot be eliminated via the heat treatment or sintering process totally. As a result, the BT-based ceramic prepared by the solid-state powders has an absolute advantage in accelerating aging failure performance, compared to that prepared hydrothermal powders. The TSDC results indicate that the ceramic prepared by the solid-state powders has a lower oxygen vacancy concentration and a higher activation energy. Furthermore, a scaling analysis based on a RC equivalent model identifies the longer oxygen vacancy diffusion time for the ceramic prepared by the solid-state powders. All these features demonstrate that the solid-state ultra-fine BT powders are a promising candidate for the fabrication of the ultra-thin layer MLCCs.