nators and filters, but also in products and the like such as sensors and actuators that use electric charge and displacement.The conventional piezoelectric ceramics are generally ferroelectrics having a perovskite structure, such as lead titanate zirconate of the tetragonal system or trigonal system (PbZrO.sub.3-PbTiO.sub.3 solid solution, hereinafter referred to asPZT), or lead titanate of the t