Characterisation and electroacoustic Modelling of porous piezoceramics with graded porosity for ultrasonic transducer applications

In this study, a characterisation method for graded porosity piezoceramic discs is presented. A sample with graded porosity from about 5 to about 40% along the thickness has been produced. Two homogeneous samples with respectively low and high porosity are used as references. Density measurements have been performed in order to estimate the average porosity of samples. Using an equivalent circuit model including the mechanical and dielectric losses and a fitting technique, the electroacoustic properties of the constant porosity samples have been extracted. Then, based on a model of multilayer piezoceramics, the graded porosity sample properties are simulated assuming it is made of 10 layers stacked along the sample thickness