JP-2026076086-A - Piezoelectric elements and their applications

Abstract

[Problem] To provide a lead-free piezoelectric element that exhibits excellent piezoelectric properties and superior dielectric breakdown strength. [Solution] A piezoelectric element comprising a piezoelectric ceramic layer mainly composed of an alkali niobate perovskite oxide and an internal electrode mainly composed of Ni, which are alternately stacked, wherein the alkali niobate perovskite oxide contains a first metal element which is at least one of Ni, Cu, and Ag, and the piezoelectric ceramic layer has an inert layer located at the end face in the stacking direction and an active layer located inside in the stacking direction, wherein the concentration [mol%] of the first metal element contained in the alkali niobate perovskite oxide in the active layer is higher than the concentration [mol%] of the first metal element contained in the alkali niobate perovskite oxide in the inert layer. [Selection Diagram] Figure 1

Inventors

• 廣瀬 吉進
• 市橋 健太郎
• 中川 功貴
• 丸山 広司

Assignees

• 日本特殊陶業株式会社

Dates

Publication Date

20260511

Application Date

20241023

Claims (8)

1. A piezoelectric element comprising a piezoelectric ceramic layer mainly composed of an alkali niobate perovskite oxide and an internal electrode mainly composed of Ni, which are alternately stacked, The alkali niobate perovskite-type oxide contains a first metal element which is at least one of Ni, Cu, and Ag. The piezoelectric ceramic layer is An inert layer located at the end face in the stacking direction, The active layer located inside the stacking direction, It has, The concentration [mol%] of the first metal element contained in the alkali niobate perovskite oxide in the active layer is higher than the concentration [mol%] of the first metal element contained in the alkali niobate perovskite oxide in the inert layer. A piezoelectric element characterized by the following features.
2. In the piezoelectric element according to claim 1, The first metal element includes Ni, A piezoelectric element characterized by the following features.
3. In the piezoelectric element according to claim 1, In the active layer, the ratio of the first metal element to Nb contained in the alkali niobate perovskite oxide (first metal element [mol%] / Nb [mol%]) is 0.1% or more and 3.0% or less. In the inert layer, the ratio of the first metal element to Nb contained in the alkali niobate perovskite oxide (first metal element [mol%] / Nb [mol%]) is 0.05% or less. A piezoelectric element characterized by the following features.
4. In the piezoelectric element according to claim 1, The piezoelectric ceramic layer further contains an oxide comprising at least one of Mn and Ti. A piezoelectric element characterized by the following features.
5. In the piezoelectric element according to claim 1, The aforementioned alkali-based perovskite-type oxide of niobate contains at least one of Mn and Ti. A piezoelectric element characterized by the following features.
6. A component comprising a piezoelectric element according to any one of claims 1 to 5.
7. An apparatus comprising the component described in claim 6.
8. The apparatus according to claim 7, wherein the apparatus is one of an actuator, a haptic, a buzzer, and an ultrasonic sensor.

Description

This disclosure relates to piezoelectric elements. Multilayer piezoelectric elements have been known for some time. Generally, piezoelectric elements containing lead-containing PZT-based (lead zirconate titanate) ceramics are used. However, lead can have adverse effects on the environment. Therefore, lead-free multilayer piezoelectric elements have been proposed, for example, as described in Patent Documents 1 and 2. Patent No. 5862983Patent No. 6094682 This is a schematic cross-sectional view showing the general configuration of a piezoelectric element.This is a schematic diagram showing an example of the general configuration of an actuator as a device.This is a cross-sectional view showing an example of the schematic configuration of a haptics device.This is a cross-sectional view showing an example of the general configuration of a buzzer as a device.This is a cross-sectional view showing an example of the schematic configuration of an ultrasonic sensor as a device. A. Embodiments: Figure 1 is a schematic cross-sectional view showing the general configuration of a piezoelectric element 100 as one embodiment of the present disclosure. The piezoelectric element 100 of this embodiment is composed of a laminate 90 having a substantially rectangular parallelepiped external shape, with a substantially square shape when viewed from above. For convenience, in the drawings of the present disclosure, the thickness of each layer of the laminate 90 is shown to be thicker than it actually is, and the number of layers is shown to be less than it actually is. The piezoelectric element 100 comprises a piezoelectric ceramic layer 10, a plurality of internal electrodes 20, and a pair of external electrodes 30. The piezoelectric ceramic layer 10 mainly contains an alkali niobate perovskite-type oxide. In this disclosure, "main component" means a component that accounts for 50% or more by volume. The piezoelectric ceramic layer 10 is substantially lead-free. A detailed explanation of the material composition of the piezoelectric ceramic layer 10 will be given later. The piezoelectric ceramic layer 10 has an inert layer 12 and an active layer 14. The inert layer 12 and the active layer 14 are formed by laminating and sintering multiple piezoelectric ceramic sheets. The inert layer 12 is located at the end face S1 in the stacking direction D1. In this disclosure, "inert layer 12" refers to a layer of the piezoelectric ceramic layer 10 located outside the layers of the internal electrodes 20 at both ends in the stacking direction D1. Therefore, one surface of the inert layer 12 in the stacking direction D1 is in contact with the internal electrodes 20, while the other surface of the inert layer 12 in the stacking direction D1 is not in contact with the internal electrodes 20. The piezoelectric ceramic layer 10 of this embodiment has two inert layers 12 located at both ends in the stacking direction D1, but one of the inert layers 12 may be omitted. The active layer 14 is located inside the piezoelectric ceramic layer 10 in the stacking direction D1. The active layer 14 is formed from multiple layers, each layer sandwiched between the internal electrodes 20 in the stacking direction D1. In this disclosure, "active layer 14" refers to the layer of the piezoelectric ceramic layer 10 located inside the layers of the internal electrodes 20 at both ends in the stacking direction D1. The active layer 14 is displaced when a voltage is applied. Multiple internal electrodes 20 are stacked alternately with each layer of the piezoelectric ceramic layer 10. Each set of internal electrodes 20 includes multiple electrodes 22 connected to one of a pair of external electrodes 30, and multiple electrodes 24 connected to the other of the pair of external electrodes 30. The piezoelectric ceramic layer 10 and the electrodes 22 and 24 of the internal electrodes 20 are stacked in the order of piezoelectric ceramic layer 10, electrode 22, piezoelectric ceramic layer 10, electrode 24, and this structure is repeated according to the number of layers. The internal electrode 20 of this embodiment contains Ni (nickel) as its main component. By containing Ni as the main component of the internal electrode 20, the manufacturing cost of the piezoelectric element 100 can be suppressed compared to a configuration containing noble metals such as Pd (palladium) or Pt (platinum) as the main component. In addition to the main component Ni, the internal electrode 20 may also contain one or more other elements such as Ag (silver), Cu (copper), Pd (palladium), or Pt (platinum). The external electrode 30 of this embodiment is formed primarily of Au (gold), but is not limited to Au; it may also contain metals such as Pt, Ag, Pd, Ni, or Cu as its main component, or it may be formed from an alloy of these metals, such as Ag-Pd (silver-palladium). When a voltage is applied between the pair of external electrodes 30, the piezoelectric ceramic layer 10 expands and contract