# US 2017/0288126 A1 · Piezoelectric element

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- Number: US 2017/0288126 A1
- Document ID: US20170288126A1
- Status: Published application
- Kind: A1
- Application number: 15/473,989
- Filed: 2017-03-30
- Published: 2017-10-05
- Earliest claimed: 2016-03-30
- Assignees: NGK Insulators, Ltd.
- Applicants: Ngk Insulators, Ltd.
- Inventors: Masayuki UETANI; Takatomo OGATA; Akifumi MORISHITA
- Web page: https://patentgrep.com/patent/US20170288126A1

## CPC

- H10N 30/508: {adapted for alleviating internal stress, e.g. cracking control layers}
- H10N 30/871: {Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes}
- H10N 30/067: Forming single-layered electrodes of multilayered piezoelectric or electrostrictive parts
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

The piezoelectric element comprises a piezoelectric body extending in a lateral direction and a first and second electrodes that are provided on the piezoelectric body. The piezoelectric body has an active portion sandwiched between the first and second electrodes in a thickness direction that is vertical to the lateral direction, and an inactive portion connected to the active portion in the lateral direction. The first electrode has an active electrode portion disposed on the active portion. The active electrode portion includes an interface region that is adjacent to the interface of the active portion and the inactive portion in the lateral direction, and an inner region that is separated from the interface of the active portion and the inactive portion in the lateral direction. The cross sectional surface area per unit length of the interface region in the cross section of the active electrode portion is greater than the cross sectional area per unit length of the inner region.

## Claims

### Claim 1

A piezoelectric element comprising;
a piezoelectric body extending in a lateral direction, and
a first and second electrodes provided on the piezoelectric body,
the piezoelectric body having an active portion sandwiched between the first and second electrodes in a thickness direction vertical to the lateral direction, and an inactive portion connected to the active portion in the lateral direction,
the first electrode having an active electrode portion disposed on the active portion,
the active electrode portion including an interface region adjacent to the interface of the active portion and the inactive portion in the lateral direction, and an inner region separated from the interface of the active portion and the inactive portion in the lateral direction,
a cross sectional surface area per unit length of the interface region in the cross section of the active electrode portion being greater than a cross sectional area per unit length of the inner region.

### Claim 2 (depends on 1)

The piezoelectric element according to claim 1, wherein
a surface coverage of the active portion by the interface region is greater than a surface coverage of the active portion by the inner region.

### Claim 3 (depends on 2)

The piezoelectric element according to claim 2, wherein
the surface coverage of the active portion by the interface region is greater than or equal to 90%, and
the surface coverage of the active portion by the inner region is less than or equal to 85%.

### Claim 4 (depends on 1)

The piezoelectric element according to claim 1, wherein
a thickness of the interface region is greater than a thickness of the inner region.

### Claim 5 (depends on 4)

The piezoelectric element according to claim 4, wherein
the thickness of the interface region is greater than or equal to 1.2 μm, and
the thickness of the inner region is less than or equal to 0.9 μm.

### Claim 6 (depends on 1)

The piezoelectric element according to claim 1, wherein
a thickness of the active portion is less than or equal to 2.0 μm

### Claim 7 (depends on 1)

The piezoelectric element according to claim 1 configured to be driven by an applied electrical field of greater than or equal to 0.4 kV/mm.