Ultrasonic transducer
AssigneeNGK Insulators, Ltd.
InventorsYoshihiko Ishida, Yuji Asai, Makoto Tani
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Abstract
A phase-insensitive ultrasonic transducer has a zinc oxide single crystal as a piezoelectric semiconducting acoustoelectric element, providing high sensitivity and operable over a range of wavelengths of the ultrasonic waves. The electrical conductivity of said zinc oxide single crystal may be selected in the range 10.sup.-8 to 10.sup.-2 .OMEGA..sup.-1.cm.sup.-1. The single crystal can have an attenuation rate for ultrasonic waves of 10 MHz of at least 0.8 cm.sup.-1.
Claims20
An acoustoelectric ultrasonic wave sensing element comprising a zinc oxide single crystal in which ultrasonic waves are transduced into electric voltage accompanied by phonon-charge carrier interaction.
An ultrasonic transducer comprising a zinc oxide single crystal having a pair of opposite faces to which a pair of electrodes are attached, wherein a thickness d between said opposite faces and an electrical conductivity .sigma. of said crystal satisfy the following:
- 10.sup.-8 (.OMEGA.cm).sup.-1 21 .sigma.<10.sup.-2 (.OMEGA.cm).sup.-1
- and ##EQU6## .epsilon. being the dielectric constant of said zinc oxide single crystal and v being the velocity of sound in said zinc oxide single crystal.
An ultrasonic detection apparatus having an acoustoelectric ultrasonic sensing transducer comprising a zinc oxide single crystal having a pair of opposite faces to which a pair of electrodes are attached, and means for detecting electrical signals induced at said pair of electrodes by ultrasonic waves in said crystal, wherein said electrical signals include signals into which said ultrasonic waves are transduced accompanied by phonon-charge carrier interaction.
An ultrasonic measuring apparatus having an ultrasonic transmitter, means for causing said transmitter to emit ultrasonic waves, an acoustoelectric ultrasonic sensing transducer comprising a zinc oxide single crystal having a pair of opposite faces to which a pair of electrodes are attached, and means for detecting electrical signals induced at said pair of electrodes by ultrasonic waves in said crystal, wherein said electrical signals include signals into which said ultrasonic waves are transduced accompanied by phonon-charge carrier interaction.
A method of converting ultrasonic energy into electrical signals wherein a piezoelectric semiconducting zinc oxide single crystal is employed as a transducer in which acoustoelectric energy conversion occurs without photoconduction.
A method of detection of ultrasonic waves comprising:
- sensing said waves by means of an ultrasonic sensing transducer comprising a zinc oxide single crystal having a pair of opposite faces to which a pair of electrodes are attached, wherein a thickness d between said opposite faces and an electrical conductivity .sigma. of said crystal satisfy the following:
- 10.sup.-8 (.OMEGA.cm).sup.-1 <.sigma.<10.sup.-2 (106 cm).sup.-1
- and ##EQU7## .epsilon.being the dielectric constant of the zinc oxide single crystal and v being the velocity of sound in the zinc oxide single crystal;
- and
- monitoring electrical signals generated between said pair of electrodes.
Dependencies are inferred from the claim text.