Piezoelectric film and piezoelectric ceramics
An object is to cause a piezoelectric film to perform a piezoelectric operation at a higher voltage than the conventional piezoelectric film. An aspect of the present invention is a piezoelectric film, wherein a voltage at which a piezoelectric butterfly curve that is a result obtained by measuring a piezoelectric property of a piezoelectric film takes a minimum value is larger by 2 V or more than a coercive voltage of a hysteresis curve that is a result obtained by measuring a hysteresis property of said piezoelectric film. The piezoelectric film includes an anti-ferroelectric film, and a ferroelectric film formed on the anti-ferroelectric film.
1. A piezoelectric film, wherein a voltage at which a piezoelectric butterfly curve that is a result obtained by measuring a piezoelectric property of a piezoelectric film takes a minimum value is larger by 2 V or more than a coercive voltage of a hysteresis curve that is a result obtained by measuring a hysteresis property of said piezoelectric film,
wherein said piezoelectric film comprises an anti-ferroelectric film, and a ferroelectric film formed on said anti-ferroelectric film.
2. The piezoelectric film according to claim 1 , wherein said
anti-ferroelectric film is a Pb(Zr 1-A Ti A )O 3 film,
said ferroelectric film is a Pb(Zr 1-x Ti x )O 3 film, and
said A and said x satisfy the following Formula 1 and Formula 2;
0≤A≤0.1 Formula 1
0.1< x< 1. Formula 2
3. The piezoelectric film according to claim 2 , wherein said Pb(Zr 1-x Ti x )O 3 film is a film which is formed by laminating a plurality of Pb(Zr, Ti)O 3 films having different Zr/Ti ratios, and a ratio of Zr to Ti in the whole of said laminated films satisfies the following Formula 3;
55/45≤ Zr/Ti. Formula 3
4. The piezoelectric film according to claim 3 , wherein
when a thickness of said laminated films is less than 1.0 μm, a ratio of Zr to Ti in the whole of said laminated films satisfies the following Formula 4, and
when a thickness of said laminated films is 1.0 μm or more, a ratio of Zr to Ti in the whole of said laminated films satisfies the following Formula 5;
55/45≤ Zr/Ti≤ 65/35 Formula 4
60/40≤ Zr/Ti≤ 75/25. Formula 5
5. The piezoelectric film according to claim 2 wherein
said A is 0, and
said Pb(Zr 1-A Ti A )O 3 is a PbZrO 3 film.
6. The piezoelectric film according to claim 1 wherein an element having said piezoelectric film can be caused to perform bipolar diving at a frequency of 100 Hz or more.
7. Piezoelectric ceramics comprising the piezoelectric film according to claim 2 , and
an oxide film formed under said Pb(Zr 1-A Ti A )O 3 film.
8. The piezoelectric ceramics according to claims 7 , wherein said oxide film is a SrRuO 3 film or a Sr(Ti, Ru)O 3 film.
9. The piezoelectric ceramics according to claim 7 further comprising an electrode film formed under said Pb(Zr 1-A Ti A )O 3 film.
10. The piezoelectric ceramics according to claim 9 , wherein said electrode film comprises an oxide or a metal.
11. The piezoelectric ceramics according to claim 9 , wherein said electrode film is a Pt film of an Ir film.
12. The piezoelectric ceramics according to claim 9 , further comprising a ZrO 2 film formed under said electrode film.
13. The piezoelectric ceramics according to claim 12 , further comprising a Si substrate formed under said ZrO 2 film.