Effect of CuO addition on the electrical and dielectrical properties of semiconducting barium titanate ceramics

Abstract

A number of studies [1-5] on barium titanate ceramiccapacitors with grain boundary barrier layers (referred to as GBBL capacitors) have been made in order to produce materials with the large capacitances necessary for the miniaturization of electronic circuits. The GBBL capacitors, which may be characterized by the structure consisting of sintered conductive grains with highly insulating thin layers along the grain boundaries, have mainly been prepared in the following three ways: 1. sintering high purity BaTiO3 in a reducing ambient (hydrogen or nitrogen/hydrogen) atmosphere to obtain the semiconducting ceramic bodies, followed by back oxidation of the bodies in an oxidiizing ambient (oxygen or air) atmosphere to form oxidized intergranular barrier layers; 2. making v;dence-controlled semiconducting barium titanate ceramics using a conventional procedure for the preparation of ceramics and then forming an insulating barrier layer by a second firing of the ceramics with appropriate metal oxides painted on the ceramic surfaces; 3. using a single.fire process, in which both an n-dopant (Sb203 for instance) and a p-dopant (CuO for instance) are simultaneously doped in barium titanate host materials to produce semiconducting ceramic bodies with an insulating grain boundary phase formed by precipitation of the p-dopant during cooling of the sintering process. It should be important to clear the behaviour patterns of both the electrical and the dielectrical grain boundary properties in barium titanate GBBL ceramics from the view points of both theory and the application, though