Ferroelectric Properties of CuAg/(Bi0.37Na0.37Sr0.26)TiO3 Multilayer Ceramic Actuator

This study proposes a new fabrication process that uses a mixture of base and noble metals (Cu and Ag) as an inner electrode to be co-fired in air for fabrication of the electrode/ceramic multilayer device. In order to protect... [ view full abstract ]

This study proposes a new fabrication process that uses a mixture of base and noble metals (Cu and Ag) as an inner electrode to be co-fired in air for fabrication of the electrode/ceramic multilayer device. In order to protect a base metal Cu in air flow, the Cu powders were taken in a coating process with Ag nano-particles using a wet process, and borosilicate glass using a sol-gel process, in sequence. Investigation to the degree of oxidation and shrinkage of the CuAg with glass-coating were carried out in the co-firing process. Under a binder burnout process heating to 500 °C under air atmosphere, the CuAg with glass coating survived without the formation of copper oxide. Even with further heating to 950 °C, the CuAg remained stable without oxidation. This might be due to the protection provided by the Ag layer to Cu exposure to oxidative atmosphere. The CuAg with glass coating showed a complicated shrinkage behavior, which is the similar behavior of glass in the low temperature, and the similar behavior of Ag and Cu densification in the high temperature. To measure the electrical performance of the glass-coated CuAg as an inner electrode, the CuAg/(Bi_0.37Na_0.37Sr_0.26)TiO₃ (BNST) mutilayer ceramics were prepared by a conventional tape casting and stacking procedure. The binders of the CuAg paste were evaporated out at 500 °C under air, and the sintering of the CuAg electrode was then performed at 950 °C under air. The electromechanical performance of the CuAg/BNST ceramic device is similar to that of the AgPd/BNST device, indicating that it would be possible to use as the inner electrode in a multilayer device.