Recent progress in the shaping and sintering of barium titanate nanoparticles. Application to high permittivity capacitors.

Abstract

The miniaturisation of electronic components required for many devices involves an increase their volumic efficiency. This work focus on the size reduction of capacitors. They are two ways for increasing the capacity of such passive components. One is to find materials with high permittivity, the other is to reduce the thickness of the films used in multilayers ceramics. Barium titanate, BaTiO3 (BT) nanoparticles were sintered using Spark Plasma Sintering (SPS) because the material presents interesting properties when obtained by SPS [1-3]. In this case, very unusual interesting dielectric properties, a so called “colossal” permittivity value up to several thousands. Moreover, no temperature dependence is observed. However, the values of dielectric losses are too high to consider industrial applications. In order to reduce these dielectric losses, different approaches have been proposed to control the chemistry of grain boundaries. We present here the structural, microstructural and electrical properties of ceramics sintered by SPS from BaTiO3 powders elaborated by co-precipitation method. Different routes tested to improve the dielectric properties of the ceramics are presented and discussed.On the other side, thick films of BT have been prepared. The objective of this work was to develop a BaTiO3 material having an accurate particle size to reduce the thickness of sintered films down to 1 μm. The rheological properties of the slurry have been optimized and, thanks to a suitable tape casting process, homogeneous thin films of 1 μm thickness could be obtained. Some properties of the films are described.