Patent ID: 7759846

Claim:
A piezoelectric device comprising, a piezoelectric body, and electrodes through which an electric field having strength is applied to the piezoelectric body along a predetermined direction; wherein said piezoelectric body is a monocrystalline film formed, above a substrate, of an inorganic crystalline compound containing a first ferroelectric crystal when no electric field is applied to the piezoelectric body, and having a characteristic that phase transition of at least a portion of the first ferroelectric crystal to a second ferroelectric crystal occurs when the strength of said electric field is at or above a predetermined level E 1 , the first ferroelectric crystal and the second ferroelectric crystal have structures corresponding to different crystal systems, and said piezoelectric device is driven under a condition that a minimum strength Emin, a maximum strength Emax, and the predetermined level E 1 of the electric field applied to the piezoelectric body satisfy the inequalities, Emin<E1<Emax.