US-20260130114-A1 - PIEZOELECTRIC DEVICE AND ULTRASONIC DEVICE

US20260130114A1US 20260130114 A1US20260130114 A1US 20260130114A1US-20260130114-A1

Abstract

A piezoelectric device includes: a substrate having a vibrating region and a non-vibrating region that surrounds the vibrating region; a first electrode provided across the vibrating region and the non-vibrating region; a second electrode disposed in the vibrating region to be separate from the first electrode; a piezoelectric body provided across the substrate, the first electrode, and the second electrode; and a third electrode that is disposed on the piezoelectric body and overlaps with at least the first electrode and the second electrode in the vibrating region when viewed in a thickness direction of the substrate.

Inventors

Chikara Kojima
Motoki Takabe

Assignees

SEIKO EPSON CORPORATION

Dates

Publication Date: 20260507
Application Date: 20251104
Priority Date: 20241106

Claims (9)

1 . A piezoelectric device comprising: a substrate having a vibrating region and a non-vibrating region that surrounds the vibrating region; a first electrode provided across the vibrating region and the non-vibrating region; a second electrode disposed in the vibrating region to be separate from the first electrode; a piezoelectric body provided across the substrate, the first electrode, and the second electrode; and a third electrode that is disposed on the piezoelectric body and overlaps with at least the first electrode and the second electrode in the vibrating region when viewed in a thickness direction of the substrate.
2 . The piezoelectric device according to claim 1 , wherein a width of a portion of the first electrode that is a portion disposed in the vibrating region is smaller than or equal to a width of the second electrode, and a sum of the width of the first electrode disposed in the vibrating region and the width of the second electrode is smaller than a width of the vibrating region.
3 . The piezoelectric device according to claim 2 , wherein the first electrode is provided to sandwich the second electrode in a direction intersects with the thickness direction.
4 . The piezoelectric device according to claim 3 , wherein 0 . 25 < W 1 /W 2 ≤ 1 , and 0 . 5 < (W 1 +W 2 )/Wc < 1 are satisfied, where W 1 is a sum of widths of portions of the first electrode that are disposed in the vibrating region, W 2 is the width of the second electrode, and Wc is the width of the vibrating region.
5 . The piezoelectric device according to claim 1 , comprising a voltage applicator configured to apply a voltage to a space between the first electrode and the third electrode and a voltage to a space between the second electrode and the third electrode, wherein the voltage applicator is configured to make a phase of the voltage applied to the space between the first electrode and the third electrode different from a phase of the voltage applied to the space between the second electrode and the third electrode.
6 . The piezoelectric device according to claim 5 , wherein 150 ° ≤ Δφ ≤ 210 ° is satisfied, where Δφ is a difference in phase between the voltage applied to the space between the first electrode and the third electrode and the voltage applied to the space between the second electrode and the third electrode.
7 . The piezoelectric device according to claim 1 , comprising: a support substrate disposed to face a side of the third electrode that is a side opposite the substrate; and a support leg configured to bond at least one of the substrate, the piezoelectric body, and the third electrode to the support substrate in the non-vibrating region.
8 . The piezoelectric device according to claim 7 , wherein the support substrate has a through hole in a portion where the through hole overlaps with the vibrating region in the thickness direction.
9 . An ultrasonic device comprising: the piezoelectric device according to claim 1 , wherein the ultrasonic device is configured to transmit ultrasonic waves by driving the piezoelectric device.

Description

The present application is based on, and claims priority from JP Application Serial Number 2024-194717, filed November 6, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to a piezoelectric device and an ultrasonic device. 2. Related Art There is a known piezoelectric device of related art in which a piezoelectric element is disposed at a vibrating plate and a voltage is applied to the piezoelectric element to vibrate the vibrating plate (refer, for example, to JP-A-2021-153293). The piezoelectric device described in JP-A-2021-153293 is an ultrasonic device and includes a silicon substrate having a void, a vibrating plate that is provided on the silicon substrate and covers the void, a first electrode disposed on the vibrating plate, a piezoelectric body provided at a position where the piezoelectric body overlaps with the void when viewed in the thickness direction, and a second electrode provided on the piezoelectric body. In the ultrasonic device, the piezoelectric body is so disposed that 0.65 ≤ Pw/Cw ≤ 0.95 is satisfied, where Cw is the width of the void, and Pw is the width of the piezoelectric body. JP-A-2021-153293 is an example of the related art. A piezoelectric device of related art, such as that described in JP-A-2021-153293, however, has a problem of a small amount of deformation of the vibrating plate due to the fact that the piezoelectric body to which a voltage is applied bends the vibrating plate toward the void, but does not bend the vibrating plate toward the side opposite the void. Therefore, when the piezoelectric device is used as an ultrasonic device, the amount of deformation of the vibrating plate is small, so that the ultrasonic waves output from the ultrasonic device undesirably have a low sound pressure. SUMMARY A piezoelectric device according to a first aspect of the present disclosure includes a substrate having a vibrating region and a non-vibrating region that surrounds the vibrating region; a first electrode provided across the vibrating region and the non-vibrating region; a second electrode disposed in the vibrating region to be separate from the first electrode; a piezoelectric body provided across the substrate, the first electrode, and the second electrode; and a third electrode that is disposed on the piezoelectric body and overlaps with at least the first electrode and the second electrode in the vibrating region when viewed in a thickness direction of the substrate. An ultrasonic device according to a second aspect of the present disclosure includes the piezoelectric device according to the first aspect described above, and is configured to transmit ultrasonic waves by driving the piezoelectric device. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a schematic configuration of an ultrasonic device according to a first embodiment. FIG. 2 is a plan view showing a schematic configuration of the ultrasonic device according to the first embodiment. FIG. 3 shows displacement of a vibrating region that occurs when the ultrasonic device according to the first embodiment is driven. FIG. 4 shows driving efficiency provided when (W1+W2)/Wc is changed in the first embodiment. FIG. 5 shows the drive efficiency provided when W1/W2 is changed in the first embodiment. FIG. 6 shows the drive efficiency provided when a phase difference Δφ between a first drive voltage and a second drive voltage is changed in the first embodiment. FIG. 7 is a cross-sectional view showing a schematic configuration of an ultrasonic device according to a second embodiment. FIG. 8 is a diagrammatic view showing a schematic configuration of a head according to a third embodiment. FIG. 9 is a plan view showing a schematic configuration of a piezoelectric device according to Variation 2. DESCRIPTION OF EMBODIMENTS First embodiment A first embodiment of the present disclosure will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of an ultrasonic device that is a piezoelectric device according to the present embodiment, and FIG. 2 is a plan view showing a schematic configuration of the ultrasonic device. An ultrasonic device 10 includes a substrate 11, a first electrode 12, a second electrode 13, a piezoelectric body 14, a third electrode 15, a vibration suppressor 16, and a voltage controller 20, as shown in FIG. 1. Note that FIG. 2 does not show the piezoelectric body 14 and the third electrode 15. In the present embodiment, the first electrode 12 and the second electrode 13 are layered on the substrate 11, the piezoelectric body 14 is layered to cover the substrate 11, the first electrode 12, and the second electrode 13, and the third electrode 15 is layered on the piezoelectric body 14. It is assumed in the following description that the thickness direction of the substrate 11, that is, the direction in which the substrate 11, the first electrode