PROBLEM TO BE SOLVED: To make output sound pressure in wave transmission of a desired high-frequency component or an output voltage in wave reception larger than them in a primary mode.SOLUTION: A piezoelectric layer 24 has electrodes on surfaces of piezoelectric bodies between layers and at both ends thereof, and outputs and receives electric signals through the electrodes. Defining the relation of a piezoelectric body in a (4P+1)th stage from a fixed end side as reference relation between electric displacement due to piezoelectric positive effect or the sign of an electric field, and the direction of residual polarization or a crystal axis while the piezoelectric bodies each have residual polarization in a thickness direction, the piezoelectric bodies are so arranged that piezoelectric bodies in the (4P+2)th stage adjoining it and the (4P+3)th stage thereabove has periodicity in the opposite relation from the reference relation, and the piezoelectric body in the (4P+4)th stage further thereabove has periodicity in the same relation as teh reference relation. A dematching layer 23 which is adapted to reflect vibration propagated from the piezoelectric layer 24 to the fixed end side, and has larger acoustic impedance than the piezoelectric layer 24 is provided on the fixed end side of the piezoelectric layer 24.COPYRIGHT: (C)2013,JPO&INPIT【課題】所望高周波成分の送波時の出力音圧あるいは受波時の出力電圧が1次モードのそれらよりも大きくなるようにする。【解決手段】圧電層24は、その層間及び両端の圧電体の表面に電極を有し、該電極によって電気信号の入出力を行う。圧電体は、それぞれ厚み方向に残留分極を有し、圧電正効果による電気変位又は電場の符号と残留分極の向きあるいは結晶軸との関係について、固定端側から4P+1段目となる圧電体における関係を基準関係としたとき、これに接する4P+2段目及びその上の4P+3段目の圧電体では基準関係とは反対の関係、さらにその上の4P+4段目の圧電体では基準関係と同一の関係となる周期性を持つように配列される。圧電層24から固定端側に伝播する振動を反射させるための、圧電層24よりも音響インピーダンスの大きいデマッチング層23を、圧電層24の固定端側に設ける。【選択図】図25
