EP-4113552-B1 - CERAMIC CAPACITOR COMPRISING TWO CRYSTAL GRAIN SIZES BASED ON BARIUM TITANATE AND ADDITIVE

Inventors

• NAGAYOSHI, Maiko

Dates

Publication Date

20260506

Application Date

20210201

Claims (3)

1. A capacitor (100), comprising: a stack (1) including a plurality of dielectric layers (5) and a plurality of internal electrode layers (7) alternately stacked on one another; and an external electrode (3) on a surface of the stack (1), the external electrode (3) being electrically connected to the plurality of internal electrodes, the plurality of dielectric layers (5) including crystal grains (6) comprising barium titanate and an additive element, the crystal grains (6) including first crystal grains (6A) and second crystal grains (6B) having a grain size larger than the first crystal grains (6A), the first crystal grains (6A) satisfying 0.13 µm ≤ d1 < 0.30 µm, where d1 is a grain size of the first crystal grains (6A), the second crystal grains (6B) satisfying 0.30 µm ≤ d2 < 0.50 µm, where d2 is the grain size of the second crystal grains (6B), the second crystal grains (6B) having a higher additive element content than the first crystal grains (6A), wherein the second crystal grains (6B) have an area percentage of 4 to 18% inclusive per unit area in a cross section of the plurality of dielectric layers (5).
2. The capacitor (100) according to claim 1, wherein the second crystal grains (6B) continuous with one another in a cross section of the plurality of dielectric layers (5) are two or fewer second crystal grains (6B).
3. The capacitor (100) according to claim 1 or claim 2, wherein the additive element includes at least one selected from the group consisting of dysprosium, magnesium, and calcium.

Description

TECHNICAL FIELD The present disclosure relates to a stacked capacitor. BACKGROUND OF INVENTION A known technique is described in, for example, Patent Literature 1. Patent Literature 2 discloses a capacitor comprising a dielectric layer composed of a dielectric ceramic including first crystal grains containing barium titanate as a primary component, and second crystal grains of strontium zirconate, and containing at least one rare earth element selected from a group consisting of terbium, dysprosium, holmium, erbium and gadolinium. The first crystal grains include at least two kinds of crystal grains having a difference of 0.1 atom% or larger therebetween in the concentration of the rare earth element at a depth of 20 nm from a grain boundary. CITATION LIST PATENT LITERATURE Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2005-243890; Patent Literature 2: JP 2014 090119 A SUMMARY The present invention provides a capacitor according to claim 1. Further embodiments are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS The objects, features, and advantages of the present disclosure will be more apparent from the detailed description and the drawings below. FIG. 1 is an external perspective view of a capacitor.FIG. 2 is a cross-sectional view taken along a section line II-II in FIG. 1.FIG. 3 is an enlarged schematic cross-sectional view of a dielectric layer.FIG. 4 is an enlarged schematic view of a second crystal grain. DESCRIPTION OF EMBODIMENTS A capacitor with the structure that forms the basis of a capacitor according to one or more embodiments of the present disclosure is an electric component included in an electronic device. The capacitor is to have higher capacitance and improved various characteristics. For example, the stacked ceramic capacitor described in Patent Literature 1 includes dielectric layers including two different types of grains with mean grain sizes meeting a specific relationship between them. This capacitor has higher capacitance as well as improved withstand voltage and DC (direct current) bias characteristics. A capacitor according to one or more embodiments of the present disclosure will now be described with reference to the drawings. The capacitor according to one or more embodiments of the present disclosure is not limited to the specific embodiments described below. The capacitor according to one or more embodiments of the present disclosure may be embodied in various forms without departing from the scope of the general idea defined by the appended claims. FIG. 1 is an external perspective view of a capacitor. FIG. 2 is a cross-sectional view taken along a section line in FIG. 1. A capacitor 100 according to an embodiment of the present disclosure includes a stack 1 and external electrodes 3 on the surfaces of the stack 1. The stack 1 includes dielectric layers 5 and internal electrode layers 7 that are stacked alternately. The stack 1 in the present embodiment is, for example, a rectangular prism and includes the dielectric layers 5 and the internal electrode layers 7 both being rectangular in a plan view in the stacking direction. Each internal electrode layer 7 has one side exposed on one side surface of the stack 1. The external electrodes 3 covering the side surfaces of the stack 1 are electrically connected to the internal electrode layers 7. Although FIG. 2 illustrates a stack of several dielectric layers 5 and several internal electrode layers 7 to simplify the drawing, the stack 1 may include, for example, several hundred dielectric layers 5 and several hundred internal electrode layers 7. FIG. 3 is an enlarged schematic cross-sectional view of a dielectric layer. Each dielectric layer 5 includes crystal grains 6 containing barium titanate and an additive element. The crystal grains 6 include first crystal grains 6A and second crystal grains 6B having a larger grain size than the first crystal grains 6A. The crystal grains 6 contain barium titanate as a main component and an additive element. A main component herein refers to a component with the highest content in the crystal grains 6. The crystal grains 6 containing barium titanate as a main component thus refer to the crystal grains 6 having higher contents of titanium and barium than other components. The additive element is at least one selected from the group consisting of dysprosium (Dy), magnesium (Mg), calcium (Ca), manganese (Mn), and silica (Si). The additive element contained in the crystal grains 6 is, for example, diffused in the crystals of barium titanate. The crystal grains 6 include the first crystal grains 6A with a smaller size and the second crystal grains 6B with a larger size. The crystal grains 6 satisfy 0.13 µm ≤ d1 < 0.30 µm and 0.30 µm ≤ d2 < 0.50 µm, where d1 is the grain size of the first crystal grains 6A and d2 is the grain size of the second crystal grains 6B. The grain size of the crystal grains 6 can be measured by analyzing an electron m