# US 2025/0098540 A1 · Piezoelectric laminate and piezoelectric element

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- Number: US 2025/0098540 A1
- Document ID: US20250098540A1
- Status: Published application
- Kind: A1
- Application number: 18/805,553
- Filed: 2024-08-15
- Published: 2025-03-20
- Earliest claimed: 2023-09-14
- Assignees: FUJIFILM Corporation
- Applicants: Fujifilm Corporation
- Inventors: Hiroyuki KOBAYASHI; Seigo NAKAMURA
- Web page: https://patentgrep.com/patent/US20250098540A1

## CPC

- H10N 30/072: by laminating or bonding of piezoelectric or electrostrictive bodies
- H10N 30/076: by vapour phase deposition
- H10N 30/50: having a stacked or multilayer structure
- H10N 30/704: {based on piezoelectric or electrostrictive films or coatings}
- H10N 30/708: {Intermediate layers, e.g. barrier, adhesion or growth control buffer layers}
- H10N 30/8554: {Lead-zirconium titanate [PZT] based}
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A piezoelectric laminate comprise: a substrate, a lower electrode layer and a piezoelectric film, in which in a case where an upper electrode layer is formed on the piezoelectric film, and a voltage applied between the upper electrode layer and the lower electrode layer is swept, in a current-voltage curve showing a change in a current with respect to a change in the voltage, which is obtained in a case where with the lower electrode layer being grounded and the upper electrode layer being used as a drive electrode, an applied voltage to the piezoelectric film is gradually increased from 0 V to a positive side and then gradually decreased from the positive side to a negative side via 0 V, the number of peaks during an increase of the voltage and the number of peaks during a decrease of the voltage are different from each other.

## Claims

### Claim 1

A piezoelectric laminate comprising:
a substrate; and
a lower electrode layer and a piezoelectric film containing a perovskite-type oxide as a main component provided in this order on the substrate,
wherein in a case where an upper electrode layer is formed on the piezoelectric film, and a voltage applied between the upper electrode layer and the lower electrode layer is swept, in a current-voltage curve showing a change in a current with respect to a change in the voltage, which is obtained in a case where with the lower electrode layer being grounded and the upper electrode layer being used as a drive electrode, an applied voltage to the piezoelectric film is gradually increased from 0 V to a positive side and then gradually decreased from the positive side to a negative side via 0 V, the number of peaks during an increase of the voltage and the number of peaks during a decrease of the voltage are different from each other.

### Claim 2 (depends on 1)

The piezoelectric laminate according to claim 1,
wherein in a case where a peak half-width during an increase of the voltage is defined as Wu, and a peak half-width during a decrease of the voltage is defined as Wd in the current-voltage curve, Wu≥1.5×Wd is satisfied.

### Claim 3 (depends on 1)

The piezoelectric laminate according to claim 1,
wherein in a case where the number of peaks during an increase of the voltage is defined as NA, and the number of peaks during a decrease of the voltage is defined as NB, NA>NB is satisfied.

### Claim 4 (depends on 3)

The piezoelectric laminate according to claim 3,
wherein the number of peaks NA during an increase of the voltage is greater than the number of peaks NB during a decrease of the voltage by 1.

### Claim 5 (depends on 3)

The piezoelectric laminate according to claim 3,
wherein the number of peaks NA during an increase of the voltage is 3, and the number of peaks NB during a decrease of the voltage is 2.

### Claim 6 (depends on 1)

The piezoelectric laminate according to claim 1,
wherein the perovskite-type oxide is represented by Pba{(ZrxTi1−x)1−yMy}O3,
where M is a metal element selected from the group consisting of V, Nb, Ta, Sb, Mo, and W, and
0<x<1, 0<y<1, and 0.9≤a≤1.2 are satisfied.

### Claim 7 (depends on 6)

The piezoelectric laminate according to claim 6,
wherein the M is Nb, and 0.08≤y≤0.15 is satisfied.

### Claim 8 (depends on 1)

The piezoelectric laminate according to claim 1,
wherein in the piezoelectric film, in a crystal grain size distribution acquired by an electron back scattered diffraction method, an average grain size obtained by performing weighted averaging with an area ratio of crystal grain sizes is 0.3 m or more.

### Claim 9 (depends on 1)

The piezoelectric laminate according to claim 1, further comprising:
a seed layer that is lattice-matched with the perovskite-type oxide between the lower electrode layer and the piezoelectric film.

### Claim 10 (depends on 9)

The piezoelectric laminate according to claim 9,
wherein the seed layer has a lattice constant of 0.39 nm to 0.405 nm in a case of being regarded as a pseudo-cubic crystal.

### Claim 11 (depends on 9)

The piezoelectric laminate according to claim 9,
wherein the seed layer contains SrRuO3 or BaRuO3 as a main component.

### Claim 12 (depends on 1)

A piezoelectric element comprising:
the piezoelectric laminate according to claim 1; and
an upper electrode layer provided on the piezoelectric film of the piezoelectric laminate.