US-20260128220-A1 - MULTILAYER CERAMIC CAPACITOR

US20260128220A1US 20260128220 A1US20260128220 A1US 20260128220A1US-20260128220-A1

Abstract

A multilayer ceramic capacitor includes a laminate including dielectric layers and first and second internal electrode layers, and first and second external electrodes respectively on first and second end surfaces. Materials of the first and second internal electrode layers are different from one another. The first internal electrode layers and the dielectric layers are Schottky-joined. The second internal electrode layers and the dielectric layers are Schottky-joined or ohmic-joined. Where no voltage is applied between the first external electrode and the second external electrode, a difference between a work function of the first internal electrode layers and a work function of the dielectric layers is greater than a difference between a work function of the second internal electrode layers and the work function of the dielectric layers.

Inventors

Ryota KARAYA

Assignees

MURATA MANUFACTURING CO., LTD.

Dates

Publication Date: 20260507
Application Date: 20251230
Priority Date: 20230630

Claims (19)

1 . A multilayer ceramic capacitor comprising: a multilayer body including a dielectric layer, a first internal electrode layer, and a second internal electrode layer, a first main surface and a second main surface opposed to each other in a lamination direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the lamination direction, and a first lateral surface and a second lateral surface opposed to each other in a width direction orthogonal or substantially orthogonal to the lamination direction and the length direction; a first external electrode connected to the first internal electrode; and a second external electrode connected to the second internal electrode; wherein a material of the first internal electrode layer and a material of the second internal electrode layer are different from each other; the first internal electrode layer and the dielectric layer define a Schottky junction; the second internal electrode layer and the dielectric layer define a Schottky junction or an ohmic contact; and in a state where no voltage is applied between the first external electrode and the second external electrode, a difference between a work function of the first internal electrode layer and a work function of the dielectric layer is greater than a difference between a work function of the second internal electrode layer and the work function of the dielectric layer.
2 . The multilayer ceramic capacitor according to claim 1 , wherein the first internal electrode layer includes Ni and Sn covering the Ni.
3 . The multilayer ceramic capacitor according to claim 1 , wherein the first external electrode includes Sn.
4 . The multilayer ceramic capacitor according to claim 1 , wherein the dielectric layer includes a plurality of different dielectric regions; and dielectric regions of the plurality of dielectric regions in contact with the first internal electrode layer are different from dielectric regions of the plurality of dielectric regions in contact with the second internal electrode layer.
5 . The multilayer ceramic capacitor according to claim 1 , wherein an appearance of the first external electrode and an appearance of the second external electrode are different from each other.
6 . The multilayer ceramic capacitor according to claim 1 , wherein the second internal electrode layer includes Ni not covered with Sn.
7 . The multilayer ceramic capacitor according to claim 1 , wherein a material of the first external electrode layer is different from a material of the second external electrode layer.
8 . The multilayer ceramic capacitor according to claim 1 , wherein each of the first and second external electrodes includes Sn; and an Sn content of the first external electrode is different from an Sn content of the second external electrode.
9 . A multilayer ceramic capacitor comprising: a multilayer body including a dielectric layer, a first internal electrode layer, and a second internal electrode layer, a first main surface and a second main surface opposed to each other in a lamination direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the lamination direction, and a first lateral surface and a second lateral surface opposed to each other in a width direction orthogonal or substantially orthogonal to the lamination direction and the length direction; a first external electrode connected to the first internal electrode; and a second external electrode connected to the second internal electrode; wherein the first internal electrode layer includes Ni and Sn covering the Ni; and the second internal electrode layer includes Ni not covered with Sn.
10 . A multilayer ceramic capacitor comprising: a multilayer body including a dielectric layer, a first internal electrode layer, and a second internal electrode layer, a first main surface and a second main surface opposed to each other in a lamination direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the lamination direction, and a first lateral surface and a second lateral surface opposed to each other in a width direction orthogonal or substantially orthogonal to the lamination direction and the length direction; a first external electrode connected to the first internal electrode; and a second external electrode connected to the second internal electrode; wherein each of the first and second external electrodes includes Sn; and an Sn content of the first external electrode is different from an Sn content of the second external electrode.
11 . The multilayer ceramic capacitor according to claim 9 , wherein the first external electrode includes Sn.
12 . The multilayer ceramic capacitor according to claim 9 , wherein an appearance of the first external electrode and an appearance of the second external electrode are different from each other.
13 . The multilayer ceramic capacitor according to claim 9 , wherein a material of the first external electrode layer is different from a material of the second external electrode layer.
14 . The multilayer ceramic capacitor according to claim 9 , wherein each of the first and second external electrodes includes Sn; and an Sn content of the first external electrode is different from an Sn content of the second external electrode.
15 . The multilayer ceramic capacitor according to claim 10 , wherein the first internal electrode layer includes Ni and Sn covering the Ni.
16 . The multilayer ceramic capacitor according to claim 10 , wherein the second internal electrode layer includes Ni not covered with Sn.
17 . The multilayer ceramic capacitor according to claim 10 , wherein each of the first and second external electrodes includes a base electrode layer and a plated layer; and the base electrode layer includes at least one of a fired layer, an electrically conductive resin layer, or a thin film layer.
18 . The multilayer ceramic capacitor according to claim 9 , wherein each of the first and second external electrodes includes a base electrode layer and a plated layer; and the base electrode layer includes at least one of a fired layer, an electrically conductive resin layer, or a thin film layer.
19 . The multilayer ceramic capacitor according to claim 1 , wherein each of the first and second external electrodes includes a base electrode layer and a plated layer; and the base electrode layer includes at least one of a fired layer, an electrically conductive resin layer, or a thin film layer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Japanese Patent Application No. 2023-108197 filed on Jun. 30, 2023 and is a Continuation Application of PCT Application No. PCT/JP2024/014058 filed on Apr. 5, 2024. The entire contents of each application are hereby incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to multilayer ceramic capacitors. 2. Description of the Related Art Multilayer ceramic capacitors that are each able to maintain capacitance even when a DC voltage is applied have been known. Japanese Unexamined Patent Application, Publication No. 2014-189464 describes using a magnetic composition represented by (Bi1-xSrx)(Fe1-yTiy)O3, where 0.2≤x≤0.7 and 0.2≤y≤0.7, and having a sintered body average particle size of 1.0 μm or less, for a material of dielectric layers included in a multilayer ceramic capacitor. However, in conventional multilayer ceramic capacitors, there is room for improvement in that the capacitance that can be maintained is not sufficient in some cases. SUMMARY OF THE INVENTION Example embodiments of the present invention provide multilayer ceramic capacitors that are each able to maintain high capacitance even when a DC voltage is applied. An example embodiment of the present invention provides a multilayer ceramic capacitor which includes a multilayer body including a plurality of dielectric layers, a plurality of first internal electrode layers, and a plurality of second internal electrode layers that are laminated, the multilayer body further including a first main surface and a second main surface opposed to each other in a lamination direction, a first end surface and a second end surface opposed to each other in a length direction orthogonal or substantially orthogonal to the lamination direction, and a first lateral surface and a second lateral surface opposed to each other in a width direction orthogonal or substantially orthogonal to the lamination direction and the length direction, a first external electrode on the first end surface, and a second external electrode on the second end surface, in which a material of the plurality of first internal electrode layers and a material of the plurality of second internal electrode layers are different from each other, each one of the plurality of first internal electrode layers and a corresponding one of the plurality of dielectric layers define a Schottky junction, each one of the plurality of second internal electrode layers and a corresponding one of the plurality of dielectric layers define a Schottky junction or an ohmic contact, and in a state where no voltage is applied between the first external electrode and the second external electrode, a difference between a work function of each of the plurality of first internal electrode layers and a work function of each of the plurality of dielectric layers is greater than a difference between a work function of each of the plurality of second internal electrode layers and the work function of each of the plurality of dielectric layers. According to example embodiments of the present invention, multilayer ceramic capacitors that are each able to maintain high capacitance even when a DC voltage is applied are provided. The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a multilayer ceramic capacitor according to an example embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line I-I in FIG. 1. FIG. 3 is a cross-sectional view taken along the line II-II in FIG. 1. FIG. 4 is an explanatory diagram showing an enlarged portion of FIG. 2. FIG. 5 is a graph showing the relationship between DC voltage and capacitance. DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS Example embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view of a multilayer ceramic capacitor 1 according to an example embodiment of the present invention. The multilayer ceramic capacitor 1 includes a multilayer body 2 and external electrodes. The external electrodes include a first external electrode 20a and a second external electrode 20b. The multilayer body 2 includes a plurality of laminated dielectric layers and a plurality of internal electrode layers. The multilayer body 2 has a rectangular or substantially rectangular parallelepiped shape. In the multilayer body 2, the direction in which the dielectric layers and the internal electrode layers are laminated is defined as a lamination direction T. One direction orthogonal or substantially orthogonal to the lamination direction T is defined as a width direction W. The direction orthogonal or subst