JP4654478B2 - Dielectric composition and ceramic capacitor using the same - Google Patents

Description

【００８７】
【表２】

【００８８】
【表３】

【００８９】
考察
（１） 以上の結果を表１乃至表３に示す。表中、絶縁抵抗ＩＲの数値において、「ｍＥ＋ｎ」は「ｍ×１０^＋ｎ」を意味する。なお、焼結性の評価結果についてはこれらの表に示していないが、表１および表２の結果に関し、試料３８以外の試料については何ら問題はなかった。ただし、試料３８についてはＳｉＯ_２ の添加量が少ないため焼結性が悪く強度が不充分であった。
【００９０】
表１の結果から、まず誘電率、歪み率および容量温度特性のバランスが最も好ましいのが、試料１〜試料１１である。これに次いで、試料１２〜試料１８は、試料１〜試料１１に比べて第三次高調波歪み率ＴＨＤがやや大きくなるものの、他の特性についてはきわめて良好である。また、試料１９〜試料２２は、試料１〜試料１１に比べると比誘電率が若干低下するものの、他の特性についてはきわめて良好である。
【００９１】
これに対して、比較例である試料２７〜試料２９は、比誘電率は大きいが第三次高調波歪み率ＴＨＤが著しく悪化する。また、試料３０は、容量温度特性Ｙ５Ｒを満足しないし、試料３１は誘電損失ｔａｎδが著しく大きい。
【００９２】
また表２の結果から添加物については、以下のことが理解される。まず、試料３２，３３と試料３７との対比から、ＭｎＯの添加量を多くし過ぎると誘電損失ｔａｎδおよび絶縁抵抗ＩＲがともに悪化することがわかる。
【００９３】
また、試料３４，３５と試料３８，３９との対比から、ＳｉＯ_２ の添加量を多くしても少なくしても、誘電損失ｔａｎδおよび絶縁抵抗ＩＲがともに悪化することがわかる。
【００９４】
さらに、試料３５，３６と試料４０，４１との対比から、Ｖ２Ｏ５の添加量を少なくすると誘電損失ｔａｎδおよび絶縁抵抗ＩＲの何れもが悪化し、多くすると絶縁抵抗ＩＲが悪化することがわかる。
【００９５】
ちなみに、ＭｎＯに代えてＣｒＯを添加し、またＳｉＯ２に代えてＡｌ_２Ｏ_３を添加し、上記と同様の条件でそれぞれ評価したが、何れも同じ結果が得られた。またＶ_２ Ｏ_５ に代えてＭｏＯ_３ 、ＷＯ_３ 、Ｃｏ_３ Ｏ_４ をそれぞれ添加し、またその他の添加物としてｍＮｂ_２ Ｏ_５ 、Ｔａ_２ Ｏ_５ 、Ｙ_２ Ｏ_３ 、Ｌａ_２ Ｏ_３ 、ＣｅＯ_２ 、Ｇｄ_２ Ｏ_３ 、Ｄｙ_２ Ｏ_３ 、Ｈｏ_２ Ｏ_３ を添加して、上記と同様の条件でそれぞれ評価したが、何れも同じ結果が得られた。
【００９６】
（２）また、表３の結果については、図７に示す三角図において、試料４２，４７，４３，４４，５３，４６，４５，４８にて囲まれる領域、より好ましくは、試料４２，４７，５２，４９，４５，４８にて囲まれる領域のものが、全ての特性において良好である。なお、比較例である試料５６〜５９は、焼成しても緻密な焼結体が得られなかった。
【００９７】
なお、以上説明した実施形態および実施例は、本発明の理解を容易にするために記載されたものであって、本発明を限定するために記載されたものではない。したがって、上記の実施形態および実施例に開示された各要素は、本発明の技術的範囲に属する全ての設計変更や均等物をも含む趣旨である。
【００９８】
【発明の効果】
以上述べたように、本発明により得られる誘電体組成物は、焼成時の耐還元性に優れ、高誘電率および低歪み率を示すとともに容量温度特性に優れる。また、この誘電体組成物により構成された本発明のコンデンサは、高容量、高絶縁抵抗、低歪み率となり、容量温度特性が平坦であり、しかも内部電極に卑金属を用いることができる。
【図面の簡単な説明】
【図１】本発明の誘電体組成物の主成分三元組成図である。
【図２】本発明の誘電体組成物の主成分三元組成図である。
【図３】本発明の誘電体組成物の主成分三元組成図である。
【図４】本発明のコンデンサの実施形態を示す一部破断斜視図である。
【図５】実施例における試料１乃至３１の組成比を示す三元組成図である。
【図６】実施例の容量温度特性（Ｙ５Ｒ）を示すグラフである。
【図７】実施例における試料４２乃至６０の組成比を示す三角図である。
【符号の説明】
１…積層型セラミックコンデンサ
１１…内部電極
１２…誘電体層
１３…外部電極[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a dielectric composition and a ceramic capacitor using the same, and has excellent reduction resistance during firing, a high dielectric constant and a low strain ratio, and a dielectric composition excellent in capacitance-temperature characteristics and a high insulation resistance. The present invention relates to a ceramic capacitor having high capacity and low strain characteristics, flat capacity temperature characteristics, and capable of using a base metal for an internal electrode.
[0002]
[Prior art]
Dielectric compositions used for ceramic capacitors and the like include barium titanate (BaTiO₃) Having a high dielectric constant as a main component is known, but since it is a ferroelectric substance, the nonlinear characteristic of the voltage is strong, and the distortion rate is as large as -50 dB to -70 dB. For this reason, a capacitor that requires a low distortion rate, such as a capacitor for a coupling circuit, a capacitor for an acoustic circuit, or a capacitor for an image processing circuit, has BaTiO.₃System capacitors cannot be used, and film capacitors and electrolytic capacitors are exclusively used. However, such film capacitors and electrolytic capacitors are difficult to miniaturize and have problems in surface mountability.
[0003]
On the other hand, among ceramic capacitors, CaTiO₃, SrTiO₃, CaSrZrO₃, NdTiO₃Such a paraelectric material can be used for a coupling circuit, an acoustic circuit, and the like because of its low distortion rate. However, since it is a paraelectric material, the relative dielectric constant εr is as low as 30 to 200 and has a high capacity. It is difficult to obtain a capacitor.
[0004]
Therefore, as a dielectric composition exhibiting both a high dielectric constant and a low strain rate, SrTiO is used.₃, Bi₂TiO₃, CaTiO₃, PbTiO₃Has been proposed (for example, see Japanese Patent Application Laid-Open No. 3-97669).
[0005]
[Problems to be solved by the invention]
By the way, a noble metal such as platinum Pt, gold Au or silver Ag is used for the internal electrode of the ceramic capacitor, but it is desirable to use a base metal such as nickel from the viewpoint of cost.
[0006]
Since the dielectric composition described above contains bismuth Bi and lead Pb having a low vapor pressure, they are evaporated when fired in a reducing atmosphere. Therefore, although firing in an oxidizing atmosphere is a prerequisite, when firing in an oxidizing atmosphere, nickel is oxidized when a low-cost base metal, such as nickel, is used for the internal electrode. There was no choice but to use precious metals such as silver.
[0007]
The present invention has been made in view of the above-mentioned problems of the prior art, and has excellent reduction resistance during firing, a high dielectric constant and a low strain rate, and a dielectric composition excellent in capacity-temperature characteristics. Another object of the present invention is to provide a capacitor that has a high insulation resistance, a high capacity, and a low distortion characteristic, has a flat capacity-temperature characteristic, and can use a base metal for an internal electrode.
[0008]
[Means for Solving the Problems]
(1) In order to obtain a balanced dielectric composition having a large dielectric constant, a small distortion rate, and a small capacitance change rate with respect to temperature (hereinafter also referred to as flat capacitance-temperature characteristics), the present inventor Obtained the following findings as a result of intensive research.
[0009]
First, the strain rate depends on the electric field dependence and non-linear characteristics (ie, ferroelectricity) of the dielectric constant, but measures to suppress this include improving the linearity of the dielectric constant and crystal anisotropy. It is considered to be effective to reduce the ferroelectricity by reducing or to use a paraelectric phase. However, since the dielectric constant decreases when the ferroelectricity is reduced, the balance between them is important. In addition, since the paraelectric shows negative capacity-temperature characteristics and the ferroelectric shows positive capacity-temperature characteristics, the balance between the ferroelectric and paraelectric is also important for the capacity-temperature characteristics.
[0010]
Such a balance of dielectric constant, strain rate, and capacity-temperature characteristic is preferably achieved by controlling the composition molar ratio of calcium titanate, strontium titanate, and barium titanate. In the present invention, by adding barium titanate as a ferroelectric to calcium titanate (and strontium titanate) as a paraelectric, the balance between the paraelectric phase and the ferroelectric phase is achieved, and the dielectric constant is large. A dielectric composition having a small strain rate and a flat capacitance-temperature characteristic can be obtained.
[0011]
That is, as the composition molar ratio of barium titanate increases, the dielectric constant increases, but the strain rate and the capacity change rate with respect to temperature also increase. In contrast, when the composition molar ratio of strontium titanate is increased, the dielectric constant is also reduced although the strain rate is reduced. Further, when the composition molar ratio of calcium titanate is increased, the dielectric constant is also reduced although the strain rate is reduced.
[0012]
Further, when calcium titanate and strontium titanate are compared, when the composition molar ratio of calcium titanate increases, the capacity change rate with respect to temperature decreases, but the dielectric constant also decreases. On the other hand, when the composition molar ratio of strontium titanate increases, the dielectric constant increases, but the capacity change rate with respect to temperature also increases.
[0013]
(2) Based on such knowledge, the invention according to the first aspect is a dielectric composition containing at least calcium titanate, strontium titanate and barium titanate, and at least barium titanate with respect to these three composition molar ratios. The composition molar ratio is 0.3 or less, and the composition of calcium titanate, strontium titanate and barium titanate has a crystal structure of at least one of tetragonal and orthorhombic. (See FIG. 1).
[0014]
A composition composed of calcium titanate, strontium titanate and barium titanate shows an insoluble phase (cubic) in addition to these three composition ratios, but the composition ratio which mainly shows an insoluble phase. The strain ratio is not preferable because the strain rate is large, and the composition ratio mainly showing cubic crystals is not preferable because the strain rate is large and the capacity change rate with respect to temperature is large.
[0015]
Tetragonal crystals are also shown in the region rich in barium titanate, but in this region, the composition molar ratio of barium titanate is large, so the dielectric constant increases, but the distortion rate also increases. The balance with the rate is bad. Therefore, a tetragonal crystal in a region where the composition molar ratio of barium titanate is 0.3 or less is more preferable.
[0016]
In the above invention, the crystal structure of the obtained dielectric composition is not all composed of at least one of tetragonal and orthorhombic crystals, and the main crystal structure is at least one of tetragonal and orthorhombic crystals. Meaning. Therefore, even if an insoluble phase or a cubic crystal is included in a part thereof, it is included in the technical scope of the present invention.
[0017]
In particular, when calcium titanate, strontium titanate and barium titanate have a composition ratio in the vicinity of the phase transition point between tetragonal and orthorhombic, the balance between the dielectric constant and the strain rate is of course the capacitance temperature. Good characteristics (temperature coefficient).
[0018]
(3) The invention according to the second aspect is a dielectric composition containing at least calcium titanate and barium titanate, where the calcium titanate is CT and the barium titanate is BT.
(CT)_x(BT)_y(F)_1-xy (F is an optional component),
0.4 ≦ x <1, 0 <y ≦ 0.2
(See FIG. 2). The third component F is not particularly limited.
[0019]
By controlling the composition ratio between the paraelectric calcium titanate and the ferroelectric barium titanate, the balance between the paraelectric phase and the ferroelectric phase is achieved, and the dielectric constant is large and the distortion factor is small. A dielectric composition having a flat capacitance-temperature characteristic can be obtained.
[0020]
If the composition molar ratio (y) of barium titanate is large, the dielectric constant increases, but the distortion ratio also increases. Therefore, in order to balance the dielectric constant and the distortion ratio, 0 <y ≦ 0.2. Is more preferable. In addition, if the composition molar ratio (x) of calcium titanate is small, the dielectric constant increases, but the capacity change rate with respect to temperature also increases (capacitance temperature characteristic deteriorates). In order to take, it is more preferable that 0.4 ≦ x <1.
[0021]
(4) The invention according to the third aspect is a dielectric composition containing at least calcium titanate, strontium titanate and barium titanate, and at least about these three composition molar ratios.
The composition molar ratio (P) of calcium titanate is 0.5 to 0.85, the composition molar ratio (Q) of strontium titanate is 0.05 to 0.4, and the composition molar ratio (R) of barium titanate is 0. 1 to 0.2, where P + Q + R = 1 (see FIG. 3).
[0022]
By adding the barium titanate, a ferroelectric substance, to the calcium dielectric titanate and strontium titanate, the balance between the paraelectric phase and the ferroelectric phase is achieved, the dielectric constant is large, and the distortion rate is small. In addition, a dielectric composition having a flat capacitance temperature characteristic can be obtained.
[0023]
When the composition molar ratio (P) of calcium titanate is small, the dielectric constant increases, but the capacity change rate with respect to temperature tends to increase (temperature characteristics deteriorate). Moreover, when the composition molar ratio (Q) of strontium titanate is large, both the strain rate and the capacity change rate with respect to temperature tend to increase. Furthermore, when the composition molar ratio (R) of barium titanate is large, the dielectric constant increases, but the distortion rate tends to increase. Therefore, 0.55 ≦ P ≦ 0.8, 0.2 ≦ Q ≦ 0.35, and 0.12 ≦ R ≦ 0.18 in order to balance the dielectric constant, strain rate, and capacitance-temperature characteristics. In particular, a region near the phase transition point between tetragonal and orthorhombic is more preferable.
[0024]
(5) Incidentally, in the inventions according to the second and third aspects, it is more preferable that the dielectric composition includes a crystal structure of at least one of tetragonal crystal and orthorhombic crystal. A composition ratio mainly showing an insoluble phase is not preferable because the strain rate increases, and a composition ratio mainly showing cubic crystals is not preferable because the strain rate and the capacity change rate with respect to temperature are large.
[0025]
(6) In the invention according to the first to third aspects described above, various additives may be included.
(6-1) Examples of this type of additive include reduction resistance aids such as MnO and CrO. This reduction resistance aid has the effect of promoting sintering and insulation resistance (I_R), But if added in a large amount, the insulation resistance, dielectric loss (tan δ) and strain rate deteriorate, so 0.1 to 1 mol% is preferable.
[0026]
(6-2) Further, as other additives, a sintering aid such as a glass composition can be mentioned.
[0027]
As a sintering aid suitably used in the present invention, G group: SiO₂, Al₂O₃ , M group: BaO, CaO, SrO, L group: Li₂O, Na₂O, K₂O, B₂O₃It is at least 1 or more types of glass compositions chosen from these.
[0028]
In the dielectric composition of the invention, a sufficient sintered body cannot be obtained unless the firing temperature is 1340 ° C. or higher. When firing at a temperature lower than this temperature, the dielectric constant decreases and the insulation resistance IR decreases, Distortion increases. On the other hand, SiO₂, Al₂O₃ , V₂O₅, MoO₃, WO₃, Co₃O₄Although the additive has a side effect of lowering the firing temperature, there is a disadvantage that the insulation resistance IR is lowered when the addition amount is increased. In general, lowering the firing temperature has the effect of suppressing the occurrence of defects such as discontinuity or thickening of the internal electrode and the effect of suppressing oxidation and diffusion of the internal electrode. Therefore, by adding the sintering aid as in the present invention, the state of the internal electrode becomes good, and the dielectric breakdown strength reliability and the like are improved. Further, the addition of the sintering aid does not significantly affect the capacity-temperature characteristics.
[0029]
However, if added in a large amount, unevenness in sinterability occurs, insulation resistance and strain rate deteriorate, and if it is too small, the effect of low-temperature sinterability is lost, so 0.2 to 5 mol% is preferable.
[0030]
When at least one glass composition selected from the G group, M group, and L group is used as a sintering aid, the composition ratio of the G group, M group, and L group is preferably a triangular diagram (G, M , L), the composition ratio of the sintering aid is within the region (including the line) surrounded by the following points X1 to X5.
[0031]
X1: (0.0, 0.0, 1.0)
X2: (0.0, 0.5, 0.5)
X3: (0.1, 0.65, 0.25)
X4: (0.5, 0.0, 0.5)
X5: (0.65, 0.05, 0.3)
More preferably, when the composition ratio of the G group, the M group, and the L group is represented by a triangular diagram (G, M, L), the composition ratio of the sintering aid is represented by the following points X1, X6, X7, and X5. It is within the enclosed area (including on the line).
[0032]
X1: (0.0, 0.0, 1.0)
X6: (0.0, 0.2, 0.8)
X7: (0.3, 0.4, 0.3)
X5: (0.5, 0.0, 0.5)
(6-3) As other additives, V₂O₅, MoO₃, WO₃, Co₃O₄There may be mentioned at least one oxide selected from among the above. These have the effect of lowering the sintering temperature and lowering the strain rate. Above all, V₂O₅Is most preferred. If these are added in a large amount, the insulation resistance and dielectric loss are remarkably deteriorated, so 0.01 to 0.5 mol% is preferable.
[0033]
(6-4) As another additive, Nb₂O₅, Ta₂O₅, Y₂O₃, La₂O₃, CeO₂, Gd₂O₃, Dy₂O₃, Ho₂O₃There may be mentioned at least one oxide selected from among the above. It has the effect of improving the dielectric loss and lowering the distortion rate. These are preferably 0.01 to 0.2 mol%.
[0034]
(7) The dielectric composition according to the present invention described above is preferably used as a material for the dielectric layer of a ceramic capacitor having an internal electrode and a dielectric layer.
[0035]
In this case, it is more preferable that the internal electrode is made of Ni or Ni alloy. Since the dielectric composition according to the present invention is excellent in resistance to reduction, it can be sintered in a reducing atmosphere, and Ni or a Ni alloy can be used as an internal electrode, thereby reducing costs.
[0036]
The structure and the like of the ceramic capacitor are not particularly limited, and include a single plate capacitor in addition to the multilayer capacitor.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 4 is a partially broken perspective view showing an embodiment of the multilayer ceramic capacitor of the present invention.
[0038]
This multilayer ceramic capacitor 1 has a pair of external electrodes 13 in which internal electrodes 11 and dielectric layers 12 are alternately stacked and connected to each internal electrode.
[0039]
In this example, the internal electrode 11 is formed of nickel or a nickel alloy, and is not particularly limited, but the nickel alloy is 95% by weight or more of nickel and one or more alloys such as manganese, chromium, cobalt, and aluminum. Is preferred. Further, the nickel or nickel alloy may contain 0.1% by weight or less of phosphorus or the like as a trace component.
[0040]
Various conditions such as the thickness of the internal electrode 11 may be appropriately determined according to the purpose and application, but the thickness is usually 1 to 5 μm, particularly 2 to 3 μm.
[0041]
The material of the dielectric layer 12 contains calcium titanate, strontium titanate, and barium titanate. These three composition molar ratios are as described above. Such a composition is a perovskite type (ABO).₃), And the A / B (molar ratio) depends on the quality of the raw material, but if it is in the range of 0.99 to 1.02, the characteristics are sufficiently satisfied.
[0042]
Moreover, 0.1-1 mol% of reduction resistance assistants, such as MnO and CrO, are added to this dielectric composition, G group: SiO.₂, Al₂O₃ , M group: BaO, CaO, SrO, L group: Li₂O, Na₂O, K₂O, B₂O₃0.2 to 5 mol% of a sintering aid for at least one glass composition selected from V, V₂O₅, MoO₃, WO₃, Co₃O₄0.01 to 0.5 mol% of at least one oxide selected from among Nb and Nb₂O₅, Ta₂O₅, Y₂O₃, La₂O₃, CeO₂, Gd₂O₃, Dy₂O₃, Ho₂O₃It is preferable to add 0.01 to 0.2 mol% of at least one oxide selected from among the above.
[0043]
In addition, although the copper, copper alloy, nickel, nickel alloy, etc. are normally used for the external electrode 13, silver, the alloy of silver and palladium, etc. can also be used. The thickness of the external electrode 13 is arbitrary and may be appropriately determined according to the purpose and application, but is usually 10 to 50 μm.
[0044]
Further, the shape and size of such a multilayer ceramic capacitor 1 may be appropriately determined according to the purpose and application. For example, in the case of a rectangular parallelepiped shape, it is usually about 1.6 to 3.2 mm × 0.8 to 1.6 mm × 0.6 to 1.2 mm.
[0045]
The multilayer ceramic capacitor 1 of this embodiment can be manufactured as follows.
First, a dielectric layer paste, an internal electrode paste, and an external electrode paste are manufactured.
[0046]
The dielectric layer paste is produced by kneading a dielectric material and an organic vehicle corresponding to the composition of the dielectric composition described above, or as a water-based paint. The dielectric material can be appropriately selected from various compounds that become the composite oxides and oxides described above, for example, carbonates, nitrates, hydroxides, organometallic compounds, and the like, and can be used as a mixture. What is necessary is just to determine content of each compound in a dielectric material so that it may become the composition of the dielectric material layer mentioned above after baking. The dielectric material is usually used as a powder having an average particle size of about 0.1 to 3.0 μm.
[0047]
The organic vehicle is obtained by dissolving a binder in an organic solvent, and the binder used in the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. In addition, the organic solvent used at this time is not particularly limited, and may be appropriately selected from organic solvents such as terpineol, butyl carbitol, acetone, toluene, and the like according to a method to be used such as a printing method or a sheet method.
[0048]
The water-based paint is obtained by dissolving a water-soluble binder, a dispersing agent, and the like in water. The water-based binder is not particularly limited, and may be appropriately selected from polyvinyl alcohol, cellulose, water-soluble acrylic resin, emulsion, and the like. That's fine.
[0049]
The internal electrode paste is prepared by kneading the above-described organic vehicle with the above-described various conductive metals and alloys, or various oxides, organometallic compounds, resinates, and the like that become the above-described conductive material after firing. . The external electrode paste is also prepared in the same manner as this internal electrode paste.
[0050]
The content of the organic vehicle in each paste described above is not particularly limited, and may be a normal content, for example, about 1 to 5% by weight for the binder and about 10 to 50% by weight for the solvent. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary.
[0051]
When using the printing method, the dielectric paste and the internal electrode paste are laminated and printed on a substrate such as polyethylene terephthalate, cut into a predetermined shape, and then peeled off from the substrate to obtain a green chip. On the other hand, when the sheet method is used, a green sheet is formed using a dielectric paste, an internal electrode paste is printed thereon, and these are stacked to form a green chip.
[0052]
Next, the green chip is subjected to binder removal processing and firing. The binder removal treatment is performed before firing, and may be performed under normal conditions. In particular, when a base metal such as nickel or a nickel alloy is used as the conductive material of the internal electrode layer, the temperature increase rate is 5 to 5 in an air atmosphere. 300 ° C / hour, more preferably 10-100 ° C / hour, holding temperature 180-400 ° C, more preferably 200-300 ° C, temperature holding time 0.5-24 hours, more preferably 5-20 hours. To do.
[0053]
The firing atmosphere of the green chip may be appropriately determined according to the type of the conductive material in the internal electrode layer paste, but when a base metal such as nickel or a nickel alloy is used as the conductive material, the oxygen partial pressure of the firing atmosphere 1 × 10^-8~ 1x10^-12It is preferable to set it to atmospheric pressure. This is because if the oxygen partial pressure is too low, the conductive material of the internal electrode will be abnormally sintered and will be interrupted, and if the oxygen partial pressure is too high, the internal electrode will be oxidized. Moreover, the holding temperature of baking is 1100-1400 degreeC, More preferably, it is 1200-1380 degreeC. This is because if the holding temperature is too low, the densification becomes insufficient, and if the holding temperature is too high, the capacity-temperature characteristics deteriorate due to electrode discontinuity due to abnormal sintering of the internal electrode or diffusion of the internal electrode material.
[0054]
As other firing conditions, the heating rate is 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour, the temperature holding time is 0.5 to 8 hours, more preferably 1 to 3 hours, and the cooling rate. Is set to 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour, and the firing atmosphere is desirably a reducing atmosphere. As the atmosphere gas, for example, a mixed gas of nitrogen gas and hydrogen gas is humidified and used. It is desirable.
[0055]
When firing in a reducing atmosphere, it is desirable to anneal the sintered body of the capacitor chip. Annealing is a process for re-oxidizing the dielectric layer, thereby increasing the insulation resistance. The oxygen partial pressure in the annealing atmosphere is 1 × 10^-6Above atmospheric pressure, more preferably 1 × 10^-5~ 1x10^-4Atmospheric pressure. If the oxygen partial pressure is too low, it is difficult to reoxidize the dielectric layer, and if the oxygen partial pressure is too high, the internal electrode may be oxidized. The holding temperature during annealing is 1100 ° C. or lower, more preferably 500 to 1100 ° C. If the holding temperature is too low, the reoxidation of the dielectric layer is insufficient, the insulation resistance is deteriorated, and the accelerated life is shortened. On the other hand, if the holding temperature is too high, the internal electrode is oxidized and the capacity is lowered, and it reacts with the dielectric substrate, so that the capacity-temperature characteristics, the insulation resistance, and its accelerated life are deteriorated. Note that the annealing can be composed of only the temperature increasing process and the temperature decreasing process. In this case, the temperature holding time is zero, and the holding temperature is synonymous with the maximum temperature.
[0056]
Other annealing conditions include a temperature holding time of 0 to 20 hours, more preferably 6 to 10 hours, a cooling rate of 50 to 500 ° C./hour, more preferably 100 to 300 ° C./hour, and an annealing atmosphere gas. For example, it is desirable to use a humidified nitrogen gas.
[0057]
Incidentally, a wetter or the like can be used, for example, in order to humidify the nitrogen gas or the mixed gas in the binder removal processing, firing and annealing steps described above. In this case, the water temperature is preferably 5 to 75 ° C.
[0058]
Moreover, these binder removal processing, firing and annealing may be performed continuously or independently of each other. When these are performed continuously, the atmosphere is changed without cooling after the binder removal treatment, and then the firing is performed by raising the temperature to the holding temperature at the time of firing, followed by cooling and the annealing holding temperature. It is more preferable to perform the annealing process by changing the atmosphere when the temperature reaches.
[0059]
On the other hand, when these are performed independently, after firing, the temperature is raised in a nitrogen gas or humidified nitrogen gas atmosphere up to the holding temperature during the binder removal process, and then the temperature is further changed by changing the atmosphere. It is preferable to continue, and after cooling to the holding temperature of annealing, it is preferable to change to a nitrogen gas or humidified nitrogen gas atmosphere again and continue cooling. As for annealing, the temperature may be changed after raising the temperature to a holding temperature in a nitrogen gas atmosphere, or a humidified nitrogen gas atmosphere may be used for all the annealing steps.
[0060]
The capacitor fired body thus obtained is subjected to end face polishing, for example, by barrel polishing or sand blasting, and the external electrode paste is printed or transferred and fired to form external electrodes. The firing conditions of the external electrode paste are preferably, for example, about 10 minutes to 1 hour at 600 to 800 ° C. in a mixed gas of humidified nitrogen gas and hydrogen gas. Then, if necessary, a coating layer is formed on the surface of the external electrode by plating or the like.
[0061]
The ceramic capacitor 1 of this embodiment manufactured in this way is mounted on a printed board by soldering or the like and used for various electronic devices.
[0062]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. In the following examples, the characteristics of the dielectric composition itself according to the present invention and the characteristics of the multilayer ceramic capacitor using the dielectric composition as a dielectric layer were evaluated.
[0063]
Preparation of dielectric composition
Barium titanate BaTiO with a particle size of 0.1-1 μm₃, Strontium titanate SrTiO₃, Calcium titanate CaTiO₃, Manganese oxide MnO, silicon oxide SiO₂, Vanadium oxide V₂O₅If necessary, rare earth oxide (Nb₂O₅, Ta₂O₅, Y₂O₃, La₂O₃, CeO₂, Gd₂O₃, Dy₂O₃, Ho₂O₃The material powder of at least one oxide selected from the above was wet mixed by a ball mill for 16 hours and dried to obtain a dielectric material.
[0064]
Barium titanate BaTiO as the base material₃, Strontium titanate SrTiO₃, Calcium titanate CaTiO₃Is BaCO₃, CaCO₃, SrCO₃TiO₂Each of these was weighed and wet-mixed for 16 hours using a ball mill, dried, and then fired in air at a temperature of 1150 ° C. for 50 hours.
[0065]
By the way, barium titanate BaTiO₃, Strontium titanate SrTiO₃, Calcium titanate CaTiO₃The same characteristics were obtained using raw materials prepared by hydrothermal synthesis powder, oxalate method, and the like.
[0066]
For the measurement sample, 0.05% by weight of polyvinyl alcohol as a binder was added to the dielectric composition, and the binder and the dielectric composition were mixed so as to form granules. Next, 0.3 g of this granular dielectric composition was weighed and press-formed into a disk shape so as to have an outer diameter of 12 mm and a thickness of 0.5 mm.
[0067]
The molded body was heated at 300 ° C./hour, holding temperature 800 ° C., holding time 2 hours, air and a humidified nitrogen gas atmosphere (1 × 10 10^-5The binder removal treatment was performed under the conditions of (atmospheric pressure).
[0068]
Subsequently, the molded body was heated at a temperature rising rate of 200 ° C./hour, a holding temperature of 1380 ° C., a holding time of 2 hours, a cooling rate of 300 ° C./hour, a mixed gas atmosphere of humidified nitrogen gas and hydrogen gas (1 × 10^-9And fired under conditions of atmospheric pressure) to obtain a fired body having an outer diameter of about 10 mm and a thickness of 0.5 mm. Further, the fired body was held at a holding temperature of 900 ° C., a holding time of 9 hours, a cooling rate of 300 ° C./hour, and a humidified nitrogen gas atmosphere (1 × 10 10^-5Annealing was performed under the conditions of atmospheric pressure). A wetter was used for humidifying each atmospheric gas, and the water temperature was set to 35 ° C.
[0069]
By applying In—Ga to both sides of the disk-shaped fired body thus obtained, a φ6 mm electrode was formed, and this was used as a dielectric composition sample (hereinafter also referred to as a disk-shaped sample). Specific permittivity, dielectric loss, and capacitance-temperature characteristics were measured.
[0070]
Fabrication of multilayer ceramic capacitors
In parallel with this, a multilayer ceramic capacitor was produced.
First, for dielectric layer paste, 100% by weight of each dielectric material, 4.8% by weight of acrylic resin, 40% by weight of methylene chloride, 20% by weight of ethyl acetate, 6% by weight of mineral spirit and 4% by weight of acetone Were mixed with a ball mill to form a paste.
[0071]
For the internal electrode paste, 100% by weight of nickel particles having an average particle size of 0.2 to 0.8 μm, 40% by weight of an organic vehicle (8% by weight of ethylene cellulose resin dissolved in 92% by weight of butyl carbitol) Then, 10% by weight of butyl carbitol was kneaded with three rolls to form a paste.
[0072]
For the external electrode paste, 100% by weight of copper particles having an average particle size of 0.5 μm, 35% by weight of an organic vehicle (8% by weight of ethylene cellulose resin dissolved in 92% by weight of butyl carbitol), and butyl carbitol 7% by weight was kneaded to make a paste.
[0073]
Next, using the above-mentioned dielectric layer paste, 4.5 μm and 15 μm thick green sheets are formed on the PET film, and after printing the internal electrode paste on this, the green sheet is peeled off from the PET film. did. Next, a plurality of green sheets obtained in this manner were stacked and pressure-bonded to produce a green chip. The number of green sheets having internal electrodes was four.
[0074]
Next, the green chip was cut into a predetermined size and subjected to binder removal processing, firing and annealing to obtain a multilayer ceramic fired body.
[0075]
This binder removal treatment was performed under conditions of a temperature rising time of 15 ° C./hour, a holding temperature of 280 ° C., a holding time of 8 hours, and an air atmosphere. Firing is performed at a temperature rising rate of 200 ° C./hour, a holding temperature of 1380 ° C., a holding time of 2 hours, a cooling rate of 300 ° C./hour, a mixed gas atmosphere of humidified nitrogen gas and hydrogen gas (1 × 10^-9At atmospheric pressure). The annealing was performed at a holding temperature of 900 ° C., a holding time of 9 hours, a cooling rate of 300 ° C./hour, and a humidified nitrogen gas atmosphere (1 × 10^-5At atmospheric pressure). A wetter was used for humidifying each atmospheric gas, and the water temperature was set to 35 ° C.
[0076]
Next, after polishing the end face of this multilayer ceramic fired body by sandblasting, the external electrode paste is transferred to the end face, and fired at 800 ° C. for 10 minutes in a humidified nitrogen gas and hydrogen gas atmosphere to form the external electrode. Then, a multilayer ceramic capacitor sample was obtained (hereinafter also referred to as a capacitor sample). The size of each sample was 3.2 mm × 1.6 mm × 0.6 mm, the thickness of the dielectric layer was 10 μm and 3 μm, and the thickness of the internal electrode was 2.0 μm.
[0077]
For each sample of the multilayer ceramic capacitor thus obtained, the capacitance-temperature characteristic and the third harmonic distortion factor (THD) were measured.
[0078]
Evaluation items and evaluation methods
For the porcelain characteristics, the shrinkage ratio and porcelain density at the time of firing were calculated from the size and mass of the disk-shaped sample molded into a disk shape and fired, and the sinterability was evaluated from the results.
[0079]
Moreover, the electrostatic capacity and dielectric loss (tan δ) of the disc-shaped sample under conditions of 1 kHz and 1 Vrms were measured using an LCR meter. The relative dielectric constant was calculated from the obtained capacitance, electrode dimensions, and sample thickness.
[0080]
Regarding the temperature characteristics of the capacitance, when the electrostatic capacity at a voltage of 1 V is measured for a temperature range of −30 ° C. to + 85 ° C. using a disk-shaped sample and a capacitor sample using an LCR meter, and the reference temperature is 25 ° C. It was investigated whether or not the capacity change ratio of the above satisfied within ± 15% (the Y5R characteristic of the EIA standard of the Electronic Machinery Manufacturers Association). The case where it was satisfied was indicated by “◯”, and the case where it was not satisfied was indicated by “X”. Moreover, the capacity | capacitance change rate in the temperature range of -30 degreeC-+85 degreeC was measured about the representative sample 1 which satisfied this Y5R characteristic. This result is shown in FIG. 6 and shows good temperature characteristics.
[0081]
The third harmonic distortion factor (THD) was measured for the capacitor sample according to the procedure of the non-linearity measuring method of the fixed resistor of the Japan Electronic Machinery Association Standard EIAJ RC2111. The measuring device used was CLT-1 manufactured by RE TECNOLOGY AS. For all capacitor samples, the third harmonic distortion rate was measured when an AC voltage of 10 kHz was applied with an electric field strength of 0.3 V / μF.
[0082]
Composition ratio of each sample
The disk-shaped sample described above by changing the composition ratio of calcium titanate (CT), strontium titanate (ST) and barium titanate (BT) and the amount of various additives as shown in Tables 1 and 2 A capacitor sample was prepared.
[0083]
Table 1 shows MnO, V₂O₅, SiO₂Etc. (specifically, MnO = 0.5 mol%, V₂O₅= 0.05 mol%, SiO₂= 0.2 mol%), only the composition ratio of CT, ST and BT is changed, Sample 1 to Sample 26 are examples of the present invention, and Sample 27 to Sample 31 are comparative examples of the present invention. is there. Sample numbers corresponding to the respective composition ratios are shown in FIG.
[0084]
On the other hand, Table 2 fixes the composition ratio of CT, ST and BT (specifically, CT = 0.6 mol%, ST = 0.25 mol%, BT = 0.15 mol%) In this example, the type and amount of the additive are changed, sample 32 to sample 36 are examples of the present invention, and sample 37 to sample 41 are comparative examples of the present invention.
[0085]
In order to confirm the effectiveness of the sintering aid, G group: SiO₂, Al₂O₃ , M group: BaO, CaO, SrO, L group: Li₂O, Na₂O, K₂O, B₂O₃The composition ratio was changed as shown in Table 3 to prepare the multilayer capacitor sample described above. Table 3 fixes the composition ratio of calcium titanate (CT), strontium titanate (ST), and barium titanate (BT) and the addition amount of additives other than the sintering aid (specifically, CT = 0.55 mol%, ST = 0.33 mol%, BT = 0.12 mol%, MnO = 0.5 mol%, V₂O₅= 0.05 mol%), and only the composition ratios G, M, and L of the sintering aid are changed. Sample 42 to sample 55 are examples of the present invention, and sample 56 to sample 60 are the present invention. It is a comparative example.
[0086]
[Table 1]

[0087]
[Table 2]

[0088]
[Table 3]

[0089]
Consideration
(1) The above results are shown in Tables 1 to 3. In the table, in the numerical value of the insulation resistance IR, “mE + n” is “m × 10^{+ N}"Means. In addition, although the evaluation result of sinterability is not shown in these tables, there was no problem for the samples other than the sample 38 with respect to the results of Tables 1 and 2. However, for sample 38, SiO₂Since the amount of addition of was small, the sinterability was poor and the strength was insufficient.
[0090]
From the results shown in Table 1, samples 1 to 11 have the most preferable balance of dielectric constant, strain rate, and capacity-temperature characteristics. Subsequent to this, Sample 12 to Sample 18 have a slightly higher third-order harmonic distortion rate THD than Samples 1 to 11, but are very good in other characteristics. Samples 19 to 22 are very good with respect to other characteristics, although their relative dielectric constants are slightly lower than those of Samples 1 to 11.
[0091]
In contrast, Samples 27 to 29, which are comparative examples, have a large relative dielectric constant, but the third-order harmonic distortion rate THD is remarkably deteriorated. Further, the sample 30 does not satisfy the capacity-temperature characteristic Y5R, and the sample 31 has a remarkably large dielectric loss tan δ.
[0092]
Moreover, the following is understood about the additive from the result of Table 2. First, it can be seen from the comparison between Samples 32 and 33 and Sample 37 that both the dielectric loss tan δ and the insulation resistance IR deteriorate when the amount of MnO added is excessively increased.
[0093]
Further, from the comparison between the samples 34 and 35 and the samples 38 and 39, SiO 2₂It can be seen that both the dielectric loss tan δ and the insulation resistance IR are deteriorated even if the amount of addition is increased or decreased.
[0094]
Further, from the comparison between the samples 35 and 36 and the samples 40 and 41, it can be seen that when the amount of V2O5 added is decreased, both the dielectric loss tan δ and the insulation resistance IR are deteriorated, and when it is increased, the insulation resistance IR is deteriorated.
[0095]
Incidentally, CrO is added instead of MnO, and Al instead of SiO2.₂O₃Were evaluated under the same conditions as above, but the same results were obtained in all cases. V₂O₅Instead of MoO₃, WO₃, Co₃O₄And as other additives mNb₂O₅, Ta₂O₅, Y₂O₃, La₂O₃, CeO₂, Gd₂O₃, Dy₂O₃, Ho₂O₃Was added and evaluated under the same conditions as above, but the same results were obtained in all cases.
[0096]
(2) Regarding the results in Table 3, in the triangular diagram shown in FIG. 7, the region surrounded by the samples 42, 47, 43, 44, 53, 46, 45, 48, more preferably the samples 42, 47 , 52, 49, 45, and 48 are good in all characteristics. Samples 56 to 59, which are comparative examples, did not yield a dense sintered body even when fired.
[0097]
The embodiments and examples described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments and examples is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[0098]
【The invention's effect】
As described above, the dielectric composition obtained by the present invention is excellent in reduction resistance during firing, exhibits a high dielectric constant and a low strain rate, and is excellent in capacity-temperature characteristics. In addition, the capacitor of the present invention composed of this dielectric composition has a high capacity, a high insulation resistance, a low strain rate, a flat capacity-temperature characteristic, and a base metal can be used for the internal electrode.
[Brief description of the drawings]
FIG. 1 is a main component ternary composition diagram of a dielectric composition of the present invention.
FIG. 2 is a main component ternary composition diagram of the dielectric composition of the present invention.
FIG. 3 is a main component ternary composition diagram of the dielectric composition of the present invention.
FIG. 4 is a partially broken perspective view showing an embodiment of a capacitor of the present invention.
FIG. 5 is a ternary composition diagram showing the composition ratio of samples 1 to 31 in the example.
FIG. 6 is a graph showing capacity-temperature characteristics (Y5R) of an example.
FIG. 7 is a triangular diagram showing composition ratios of samples 42 to 60 in Examples.
[Explanation of symbols]
1 ... Multilayer ceramic capacitor
11 ... Internal electrode
12 ... Dielectric layer
13 ... External electrode

Claims (10)

At least calcium titanate, a dielectric composition containing barium titanate and sintering aid,
When calcium titanate is CT and barium titanate is BT, the following relational expression is satisfied :
[Expression 1]
(CT) _x (BT) _y (F) _1-xy (F is an optional component),
0.4 ≦ x <1,
0 <y ≦ 0.2
The content of the sintering aid is 0.2 mol% to 5 mol%,
The sintering aid is at least one glass composition selected from the following G group, M group and L group,
Group G: SiO ₂ , Al ₂ O ₃
M group: BaO, CaO, SrO
Group _{L: Li 2 O, Na 2 O} , K 2 O, B 2 O 3
When the composition ratios of the G group, the M group, and the L group are represented by triangular diagrams (G, M, L), the composition ratio of the sintering aid is within the region surrounded by the following points X1 to X5 (on the line). A dielectric composition).
X1: (0.0, 0.0, 1.0)
X2: (0.0, 0.5, 0.5)
X3: (0.1, 0.65, 0.25)
X4: (0.5, 0.0, 0.5)
X5: (0.65, 0.05, 0.3) A dielectric composition containing at least calcium titanate , strontium titanate , barium titanate and a sintering aid, the composition molar ratio of calcium titanate, strontium titanate and barium titanate ,
The composition molar ratio (P) of calcium titanate is 0.5 to 0.85,
The composition molar ratio (Q) of strontium titanate is 0.05 to 0.4,
The composition molar ratio (R) of barium titanate is 0.1 to 0.2,
However, P + Q + R = 1
The filling,
The content of the sintering aid is 0.2 mol% to 5 mol%,
The sintering aid is at least one glass composition selected from the following G group, M group and L group,
Group G: SiO ₂ , Al ₂ O ₃
M group: BaO, CaO, SrO
Group _{L: Li 2 O, Na 2 O} , K 2 O, B 2 O 3
When the composition ratios of the G group, the M group, and the L group are represented by triangular diagrams (G, M, L), the composition ratio of the sintering aid is within the region surrounded by the following points X1 to X5 (on the line). A dielectric composition).
X1: (0.0, 0.0, 1.0)
X2: (0.0, 0.5, 0.5)
X3: (0.1, 0.65, 0.25)
X4: (0.5, 0.0, 0.5)
X5: (0.65, 0.05, 0.3) Tetragonal or dielectric composition of claim 1, wherein it contains at least one of the crystal structure of orthorhombic. Capacitance rate of change with respect to temperature is within 15% ± at (reference temperature 25 ° C.) temperature range of at least -30 ℃ ~ + 85 ℃ according to any one of claims 1-3, characterized in that the Dielectric composition. The dielectric composition according to any one of claims 1-4, characterized in that it further comprises the reduction resistance aids. A region in which the composition ratio of the sintering aid is surrounded by the following points X1, X6, X7, and X5 when the composition ratio of the G group, the M group, and the L group is represented by a triangular diagram (G, M, L) The dielectric composition according to claim 1 , wherein the dielectric composition is inside (including on a line).
X1: (0.0, 0.0, 1.0)
X6: (0.0, 0.2, 0.8)
X7: (0.3, 0.4, 0.3)
X5: (0.5, 0.0, 0.5) _{V 2 O 5, MoO 3,} WO 3, a dielectric composition according to any one of claims 1 to 6, characterized in that further contains at least one or more oxides selected from among _Co 3 _{O 4} object. At least one oxide selected from Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Gd ₂ O ₃ , Dy ₂ O ₃ , and Ho ₂ O ₃ further dielectric composition according to any one of claims 1 to 7, characterized in that it contains. A ceramic capacitor having an internal electrode and the dielectric layer, a ceramic capacitor, wherein the dielectric layer is composed of a composition according to any one of claims 1-8. The ceramic capacitor according to claim 9 , wherein the internal electrode is made of Ni or a Ni alloy.

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