Patent ID: 7215067

Claim:
A piezoelectric actuator comprising a substrate and an epitaxial ferroelectric film provided on said substrate, wherein said epitaxial ferroelectric film satisfies a relation z/z 0 >1.003, where z is the c-axis lattice constant of the epitaxial ferroelectric film and z 0 is the c-axis lattice constant of a material constituting said epitaxial ferroelectric film in a bulk state, and wherein said epitaxial ferroelectric film also satisfies a relation 0.997<x/x 0 <1.003, where x is the a-axis lattice constant of the epitaxial ferroelectric film and x 0 is the a-axis lattice constant of a material constituting said epitaxial ferroelectric film in a bulk state, said epitaxial ferroelectric film has a thickness within a range of 100 nm to 10 μm, and said epitaxial ferroelectric film includes a lead (Pb) atom and an oxygen (O) atom as constituent atoms.