Preparation of Multilayer Semiconducting BaTiO3 Ceramics Co-Fired with Ni Inner Electrodes

概要

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A multilayer semiconducting BaTiO3 ceramics having positive temperature coefficient of resistivity (PTCR) characteristics is investigated with the aim of lowering its resistance. The multilayer BaTiO3 ceramics was fired in reducing atmosphere and reoxidized at 700 °C in air. The result reveals that the multilayer semiconducting BaTiO3 ceramics with Ni inner electrodes shows high resistance even when the thickness is lowered; however, excessive donor doping markedly decreases the resistance of BaTiO3 ceramics to a very low value. The donor in excessive amounts is considered to cancel the Ni acceptors occupying the Ti sites; these acceptors diffuse from the Ni inner electrode and increase resistivity. As a result, a multilayer BaTiO3 ceramics element ($3.2\times 2.5$ mm2) with a low resistance of 0.05 $\Omega$ is realized by using excess donor doping ($\text{Sm}=0.35$ mol %).
2007-10-15