Medical ultrasonic probe using electrostrictive-ceramics/polymer composite

A medical ultrasonic probe the sensitivity of which is controlled by a DC bias field is developed using an electrostrictive-ceramics-polymer composite as a transducer material. (1-x)Pb(Mg_1/3Nb_2/3)O₃-x PbTiO₃ electrostrictive-ceramics [(1-x)PMN-xPt] are used because they have a large electromechanical coupling factor for the thickness vibrational mode, k_t, under a practical bias field. 0.91PMN-0.09PT/polyurethane 1-3 composites (thickness 0.22 mm, 7.5 MHz) are fabricated using a dicing and filling technique. The 0.91PMN-0.09PT has no residual k_t after removing the DC bias field around room temperature. Pulse-echo experimentation shows that the echo amplitude increases with the bias field, as expected from the relationship between k_t and the bias field