| 摘要 |
A sensor or actuator includes a piezoelectric thin film device including a lower electrode, a piezoelectric thin film and an upper electrode, and a voltage detecting device connected between the lower and upper electrodes of the piezoelectric thin film device. The piezoelectric thin film is formed of an alkali niobium oxide-based perovskite material expressed by (K1-xNax)NbO3 (0<x<1), and a dependency of the piezoelectric constant d31 of the piezoelectric thin film on applied electric field [=|(d31 under 70 kV/cm)−(d31 under 7 kV/cm)|/|d31 under 70 kV/cm|] is 0.20 or less.
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