PIEZOELECTRIC DEVICE AND USING METHOD THEREOF

PROBLEM TO BE SOLVED: To ensure a stable work performance by eliminating the need for a polarization process by application of a high voltage which has been required conventionally, and by preventing the polarization deterioration owing to its use environment and aging.SOLUTION: A piezoelectric device (10) has an inclination which makes a bipolar polarization-electric field (Pr-E) hysteresis property of piezoelectric material asymmetry. The piezoelectric device includes a piezoelectric element part (28). The piezoelectric element part includes a piezoelectric material film (42) whose coercive electric field inclination factor is 20% or larger, and works with an electric field strength smaller than that of a first coercive electric field, provided that the coercive electric field inclination factor is defined by [(Ec2+Ec1)/(Ec2-Ec1)]×100[%], where Ec1 denotes the first coercive electric field smaller in absolute value, and Ec2 denotes a second coercive electric field larger in absolute value. The piezoelectric device (10) further includes a refresh-voltage application circuit (36) operable to restore the polarized state of the piezoelectric material film (42) by applying a voltage making an electric field strength which is larger than an electric field strength causing the device to work and no larger than three times the absolute value |Ec1| of the first coercive electric field, for the purpose of keeping the work performance of the device.