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/sub 1/3/Nb/sub 2/3/)O/sub 3/-xPbTiO/sub 3/ electrostrictive-ceramics ((1-x)PMN-xPt) are used because they have a large electromechanical coupling factor for the thickness vibrational mode, k/sub 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/sub 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/sub t/ and the bias field.<
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