A piezoelectric electro-acoustic transducer eliminates a negative influence caused by metal terminals upon the sound pressure and resonant frequency characteristics even when size and thickness reduction of the transducer are made. The transducer includes a piezoelectric diaphragm which includes a piezoelectric ceramic plate and a metal plate stored in a casing. The transducer also includes metal terminals in contact with the piezoelectric diaphragm and extending to the outside of the casing. The modulus of elasticity X of one metal terminal is specifically determined to be within a range defined by: ##EQU1## where E (N/m.sup.3) is the Young's modulus of one metal terminal in contact with a piezoelectric element, b (mm) is the width of part of the metal terminal extending from the inside of the casing to the outside thereof, h (mm) is the thickness of the metal terminal, and L (mm) is the length of the metal terminal.
A piezoelectric acoustic component includes a diaphragm having a substantially rectangular piezoelectric plate including front and back surfaces, an electrode disposed on the front surface, a substantially rectangular metal plate bonded to the back surface of the substantially rectangular piezoelectric plate directly or via an electrode disposed on the back surface of the substantially rectangular piezoelectric plate, an insulating cap having an upper wall, four side walls extending from the upper, a pair of support members arranged to support the diaphragm at the inside of the two of four sides walls opposed to each other, and a plate shaped substrate having a first electrode section and a second electrode section. The diaphragm is disposed the insulating cap. Two of four side edges of the diaphragm are opposed to each other and fixed to the pair of support members. A gap is formed between the other two of four side edges of the diaphragm and the cap and is sealed by elastic sealing material. An acoustic space is provided between the diaphragm and the upper wall of the insulating cap. An opening edge of the four side walls of the insulating cap is bonded to the substrate. The metal plate is electrically connected to the first electrode section. The electrode disposed on the front surface of the substantially rectangular piezoelectric plate is electrically connected to the second electrode section.
An ultrasonic wave transmitter/receiver is provided in which the transmission/reception range thereof in at least one direction is relatively narrow, and which has stable reverberation characteristics. When the thickness of a thick-walled portion is t1, the thickness of each of thin-walled portions is t2, the thickness of a side portion provided continuously with the thin-walled portion is A, x=t2/t1, and y=A/t2, this ultrasonic wave transmitter/receiver is formed so that x and y are within the range defined by the following equations:
Disclosed is a high-sensitivity flexible ceramic sensor for detecting mechanical shocks and vibrations, which comprises a metal foil of a specified thickness as a substrate, a single-crystalline thin film of a piezoelectric ceramic material such as aluminum nitride and zinc oxide having a specified thickness formed on the substrate, a metallic electrode formed on the thin ceramic film and an external circuit connecting the metal foil and the electrode with insertion of an electric meter for measuring the piezoelectric voltage changes induced in the ceramic thin film.
