Piezoelectric ceramic resonator devices

Claim 1

A PIEZOELECTRIC CERAMIC RESONATOR ELEMENT COMPRISING A THIN FLAT CIRCULAR DISK OF POLARIZED FERROELECTRIC CERAMIC MATERIAL, SAID DISK HAVING SUBSTANTIALLY PARALLEL MAJOR SURFACES, SAID MAJOR SURFACES HAVING THEREON ELECTRODES OF COPPER AND SILVER DISPOSED IN SUPERPOSED RELATION ONE ON THE OTHER, SAID COPPER ELECTRODES BEING FORMED BY THE ELECTRODELESS COPPER PLATING METHOD AND AT LEAST COVERING THE ENTIRE MAJOR SURFACES INCLUDING PIN HOLES EXISTING ON SAID SURFACES AND SAID SILVER ELECTRODES BEING DEPOSITED BY THE CHEMICAL DISPLACEMENT OF A SILVER SALT SOLUTION ON THE SURFACES OF SAID COPPER ELECTRODES, SAID DISK BEING POLARIZED UNIDIRECTIONALLY IN PARALLEL TO SAID MAJOR SURFACES AND BEING ADAPTED TO MAKE A PIEZOELECTRIC RESPONSE TO ELECTRICAL POTENTIAL GRADIENTS ACROSS SAID ELECTRODES IN A MANNER THAT THE THICKNESS-SHEAR VIBRATION MODE IS PREDOMINANT WHILE THE FLEXURAL VIBRATION MODE AND THE SUBRESONANT VIBRATION MODES ARE NEGLIGIBLE, AND SAID DISK A THICKNESS DIMENSION SO DETERMINED THAT RESONANCE OF VIBRATION IN SAID THICKNESS-SHEAR VIBRATION MODE TAKES PLACE AT A PARTICULARLY SELECTED FREQUENCY AND HAVING A DIAMETER DIMENSION SO DETERMINED THAT THE RESONANT IMPEDANCES OF THE FLEXURAL VIBRATIONS AND SUBRESONANT VIBRARTIONS ARE AT LEAST TEN TIMES LARGER THAN THE RESONANT IMPEDANCE OF THE FUNDAMENTAL THICKNESS-SHEAR VIBRATION IN A RANGE OF THE DIAMETER-THICKNESS RATIO OF FROM 7 TO 15.