Direct bonding of piezoelectric materials and its applications

The needs for piezoelectric devices such as SAW filters has been greatly increasing with the rapid growth of mobile communication systems. The requirements for the devices have been widely spreading and becoming more critical. In order to satisfy these requirements not only new designing methods but also new piezoelectric materials have to be brought into practice. New technique of direct bonding of piezoelectric materials is very promising to give us new piezoelectric characteristics. The direct bonding can be carried out by contacting the hydrated surfaces of the piezoelectric materials and by heat-treating at relatively low temperatures. Authors found that the direct bonding can be applied to wide variety of materials such as quartz, LiNbO₃, LiTaO₃, PLZT, Si, glass and so on. Some combinations of them showed new preferable piezoelectric characteristics. In this paper the possibility of the direct bonding of piezoelectric materials and its applications such as SAW filters are discussed