TECHNICAL FIELD

The present invention relates to a dielectric ceramic composition and ceramic electronic components using the dielectric ceramic composition as a dielectric layer.

BACKGROUND ART

In recent years, requirements of electronic components that are operated under a high temperature environment exceeding 150° C. have increased year by year for devices mounted in a harsh temperature environment, such as an environment around an engine room of an automobile. In particular, in an automobile market in recent years, the use of electronic control for each function has rapidly progressed, aiming at improving safety and environmental performance. Consequently, the mounting ratio of electronic devices has been increased. Of these electronic devices, an electronic device mounted in an engine room is exposed to a harsh temperature environment and thus high heat resistance in addition to high reliability has been required for the electronic components.

Conventionally, as the ceramic electronic components satisfying such requirement such as capacitors, a ceramic composition exhibiting a paraelectricity (paraelectric material) such as calcium zirconate is used for a dielectric layer of the ceramic electronic components. However, the electronic components having a dielectric layer constituted by the paraelectric material have low relative dielectric constant of the ceramic composition and thus capacitors having high capacity cannot be obtained.

Barium titanate (BaTiO3) known as a representative ceramic composition for ceramic capacitors has a high relative dielectric constant. However, barium titanate has the peak of the relative dielectric constant at a characteristic temperature referred to as a ferroelectric transition temperature and the properties are rapidly lowered at 120° C. or more.

Therefore, the development of a dielectric ceramic composition having a high relative dielectric constant even in a high temperature environment (for example, 150° C. or more) has been desired.

In recent years, in the ceramic electronic components, a base metal such as nickel and copper is frequently used as a material for internal electrodes. In the case where the base metal is used as the internal electrode layer, the dielectric layer and the internal electrodes are co-fired. In order to prevent the base metal from oxidation during firing, the ceramic electronic components including the ceramic composition constituting the dielectric layer are fired under a reducing atmosphere.

Non-Patent Literature 1 has described a dielectric ceramic composition having a tungsten bronze structure represented by a general formula M2+6M4+2Nb8O30. In this Non-Patent Literature 1, in order to obtain experimental samples, the raw materials of the ceramic composition are mixed, and thereafter the materials are fired around 1,000° C. for 15 hours. The obtained product is ground, dried, and molded, and thereafter further sintered at 1,250° C. to 1,350° C. for 5 hours to 6 hours.

In Patent Literatures 1 to 11, the dielectric ceramic compositions having various tungsten bronze structures have been studied.

CITATION LIST

Non-Patent Literature

Non-Patent Literature 1: Mat. Res. Bull., Vol. 27 (1992), pp. 677-684; R. R. Neurgaonkar, J. G. Nelson and J. R. Oliver

Patent Literatures

Patent Literature 1: Japanese Patent Application Laid-open No. 2002-211975Patent Literature 2: Japanese Patent Application Laid-open No. 2007-197277Patent Literature 3: Japanese Patent Application Laid-open No. H11-043370Patent Literature 4: Japanese Patent Application Laid-open No. 2000-169215Patent Literature 5: Japanese Patent Application Laid-open No. 2008-189487Patent Literature 6: WO 08/102608 PamphletPatent Literature 7: WO 06/114914 PamphletPatent Literature 8: Japanese Patent Application Laid-open No. 2013-180906Patent Literature 9: Japanese Patent Application Laid-open No. 2013-180907Patent Literature 10: Japanese Patent Application Laid-open No. 2013-180908Patent Literature 11: Japanese Patent Application Laid-open No. 2012-169635

SUMMARY

Technical Problem

However, in Non-Patent Literature 1, although the properties of the dielectric ceramic composition itself having the tungsten bronze structure have been studied from the academic viewpoint, the applications of the dielectric ceramic composition are not considered at all. In other words, in Non-Patent Literature 1, the dielectric ceramic composition is fired in a laboratory under a normal environmental atmosphere. However, as a result of detailed study for the dielectric ceramic composition having the tungsten bronze structure represented by the general formula conducted by the inventors of the present invention, the inventors of the present invention have found that a dielectric ceramic composition having completely different properties from those of the dielectric ceramic composition reported in Non-Patent Literature 1 is obtained in the case where firing and sintering are performed under a reducing atmosphere that has been required for dielectric ceramic compositions in recent years.

In Patent Literatures 1 to 11, the dielectric ceramic compositions having the tungsten bronze structures have also been studied. However, in any of these Patent Literatures, dielectric ceramic compositions simultaneously exhibiting the effects of “being possible to be fired under a reducing atmosphere”, “providing sufficiently a high relative dielectric constant”, “having an excellent dielectric property in a wide temperature region”, and “having a small dielectric loss” have not been obtained.

In addition to the above-described performances, for the dielectric ceramic composition, a high insulation resistance value above a certain level (for example, about 40 MΩ at 200° C.) is required for electronic components using the dielectric ceramic composition.

Therefore, an object of the present invention is to provide a dielectric ceramic composition that can be fired under a reducing atmosphere, has a high relative dielectric constant, and, in the case where the dielectric ceramic composition is used as the dielectric layer of ceramic electronic components such as a laminated ceramic capacitor, has a small change in electrostatic capacity even under a high temperature environment, for example, under a condition of 150° C. to 200° C. and small dielectric losses at 25° C. and 200° C., and further can obtain a high insulation resistance value even at 200° C., and ceramic electronic components in which the dielectric ceramic composition is used as the dielectric layer.

Solution to Problem

The above-described problems are solved by the present invention described below.

Namely, the present invention (1) provides a dielectric ceramic composition comprising: a first component; and a second component, wherein

as a content ratio relative to a total number of moles of the first component when converted into following oxides, the first component comprises an oxide of Ca of 0.00 mol % to 35.85 mol % in terms of CaO, an oxide of Sr of 0.00 mol % to 47.12 mol % in terms of SrO, an oxide of Ba of 0.00 mol % to 51.22 mol % in terms of BaO, an oxide of Ti of 0.00 mol % to 17.36 mol % in terms of TiO2, an oxide of Zr of 0.00 mol % to 17.36 mol % in terms of ZrO2, an oxide of Sn of 0.00 mol % to 2.60 mol % in terms of SnO2, an oxide of Nb of 0.00 mol % to 35.32 mol % in terms of Nb2O5, an oxide of Ta of 0.00 mol % to 35.32 mol % in terms of Ta2O5, and an oxide of V of 0.00 mol % to 2.65 mol % in terms of V2O5;

the first component comprises at least one oxide selected from the oxide of Ca, the oxide of Sr, and the oxide of Ba, at least one oxide selected from the oxide of Ti and the oxide of Zr, and at least one oxide selected from the oxide of Nb and the oxide of Ta as essential components, and, a total content ratio of the oxide of Ca in terms of CaO, the oxide of Sr in terms of SrO, and the oxide of Ba in terms of BaO is 48.72 mol % to 51.22 mol %, a total content ratio of the oxide of Ti in terms of TiO2, the oxide of Zr in terms of ZrO2, and the oxide of Sn in terms of SnO2is 15.97 mol % to 17.36 mol %, and a total content ratio of the oxide of Nb in terms of Nb2O5, the oxide of Ta in terms of Ta2O5, and the oxide of V in terms of V2O5is 31.42 mol % to 35.31 mol % relative to the total number of moles of the first component when converted into the oxides; and

as a content ratio relative to a total mass of the first component when converted into the oxides, the second component comprises at least (a) an oxide of Mn of 0.005% by mass to 3.500% by mass in terms of MnO and (b) one or both of an oxide of Cu and an oxide of Ru.

In addition, the present invention (2) provides a dielectric ceramic composition comprising: a first component; and a second component, wherein

as the first component, a compound represented by a following general formula (1):
AaM1bM2cOd(1)
(in the formula (1), A is represented by a general formula (2):
Ba1-x-ySrxCay(2)
(in the formula (2), 0≤x≤0.920 and 0≤y≤0.700); M1is at least one element selected from Ti, Zr, and Sn; M2is at least one element selected from Nb, Ta, and V; and 5.70≤a≤6.30, 1.90≤b≤2.10, 7.20≤c≤8.80, and 27.45≤d≤32.50) is included (with the proviso that, when Sn is included, a content ratio of the oxide of Sn in terms of SnO2relative to a total number of moles of the oxide of Ti in terms of TiO2, the oxide of Zr in terms of ZrO2, and the oxide of Sn in terms of SnO2is 15.00 mol % or less and when V is included, a content ratio of the oxide of V in terms of V2O5relative to a total number of moles of the oxide of Nb in terms of Nb2O5, the oxide of Ta in terms of Ta2O5, and the oxide of V in terms of V2O5is 7.50 mol % or less); and

as a content ratio relative to a total mass of the first component when the first component is converted into CaO, SrO, BaO, TiO2, ZrO2, SnO2, Nb2O5, Ta2O5, and V2O5, the second component comprises at least (a) an oxide of Mn of 0.005% by mass to 3.500% by mass in terms of MnO and (b) one or both of an oxide of Cu and an oxide of Ru.

In addition, the present invention (3) provides a dielectric ceramic composition comprising: a first component; and a second component, wherein

a compound represented by a following general formula (3):
α.Caη1M3θ1M4ϕ1Oω1-β.Srη2M3θ2M4ϕ2Oω2-γ.Baη3M3θ3M4ϕ3Oω3(3)
(in the formula (3), η1, η2, and η3 are each independently values within a range of 5.70 to 6.30; θ1, θ2, and θ3 are each independently values within a range of 0.95 to 1.05; ϕ1, ϕ2, and ϕ3 are each independently values within a range of 0.90 to 1.10; ω1, ω2, and ω3 are each independently values within a range of 27.45 to 32.50; M3is represented by a general formula (4):
Ti2-ρ-σZrρSnσ(4)
(in the formula (4), 0≤ρ≤2.0 and 0≤σ≤0.3); M4is represented by a general formula (5):
Nb8-π-ψTaπVψ(5)

(in the formula (5), 0≤π≤8.0 and 0≤ψ≤0.6); and α, β, and γ satisfy α+β+γ=1.00), and when an arbitrary point in a ternary composition diagram is represented as (α, β, γ), the compound existing within a range surrounded by line segments linking a point A=(0.05, 0.95, 0.00), a point B=(0.70, 0.30, 0.00), a point C=(0.70, 0.00, 0.30), a point D=(0.00, 0.00, 1.00), and a point E=(0.00, 0.90, 0.10) is included as the first component, and

as a content ratio relative to a total mass of the first component when the first component is converted into CaO, SrO, BaO, TiO2, ZrO2, SnO2, Nb2O5, Ta2O5, and V2O5, the second component comprises at least (a) an oxide of Mn of 0.005% by mass to 3.500% by mass in terms of MnO and (b) one or both of an oxide of Cu and an oxide of Ru.

In addition, the present invention (4) provides the dielectric ceramic composition of (3), wherein the first component is a compound existing within a range surrounded by line segments linking a point A′=(0.05, 0.95, 0.00), a point B′=(0.60, 0.40, 0.00), a point C′=(0.70, 0.20, 0.10), a point D′=(0.70, 0.10, 0.20), a point E′=(0.55, 0.00, 0.45), a point F′=(0.40, 0.00, 0.60), a point G′=(0.10, 0.10, 0.80), a point H′=(0.00, 0.00, 1.00), a point I′=(0.00, 0.40, 0.60) a point J′=(0.20, 0.40, 0.40), a point K′=(0.00, 0.70, 0.30), and a point L′=(0.00, 0.90, 0.10) in the ternary composition diagram.

In addition, the present invention (5) is the dielectric ceramic composition according to any one of (1) to (4), wherein, as the content ratio relative to the total mass of the first component when the first component is converted into CaO, SrO, BaO, TiO2, ZrO2, SnO2, Nb2O5, Ta2O5, and V2O5, the second component comprises one or both of an oxide of Cu of 0.010% by mass or more and less than 0.080% by mass in terms of CuO and an oxide of Ru of 0.050% by mass or more and less than 0.300% by mass in terms of RuO2.

In addition, the present invention (6) provides the dielectric ceramic composition of any one of (1) to (5), wherein an oxide of D (D is at least one element selected from Li, Mg, Si, Cr, Al, Fe, Co, Ni, Zn, Ga, Ge, In, W, Mo, Y, Hf, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) is included as the second component.

In addition, the present invention (7) provides the dielectric ceramic composition of any one of (1) to (6), wherein the dielectric ceramic composition comprises a tungsten bronze type crystal phase.

In addition, the present invention (8) provides the dielectric ceramic composition of any one of (1) to (7), wherein the relative dielectric constant at 25° C. is 100.0 or more.

In addition, the present invention (9) provides the dielectric ceramic composition of any one of (1) to (8), wherein a change rate in electrostatic capacity is within a range of −20.0% to 5.0% in a temperature range of −55° C. to 200° C.

In addition, the present invention (10) provides the dielectric ceramic composition of any one of (1) to (9), wherein a dielectric loss (tan δ) at 25° C. is 10.0% or less and a dielectric loss (tan δ) at 200° C. is 10.0% or less.

In addition, the present invention (11) provides the dielectric ceramic composition of any one of (1) to (10), wherein an insulation resistance value at 200° C. is 40 MΩ or more and less than 100 MΩ.

In addition, the present invention (12) provides ceramic electronic components, wherein a dielectric layer formed of the dielectric ceramic composition as described in any one of (1) to (11); and an electrode layer comprising a base metal as a conductive component.

In addition, the present invention (13) provides the ceramic electronic components of (12), wherein the base metal is at least one metal selected from nickel and copper.

In addition, the present invention (14) provides the ceramic electronic components of (12) or (13), wherein a plurality of the dielectric layers and a plurality of the electrode layers are laminated.

Advantageous Effects of Invention

According to the present invention, the dielectric ceramic composition that can be fired under a reducing atmosphere, has a high relative dielectric constant, and, in the case where the dielectric ceramic composition is used as the dielectric layer of ceramic electronic components such as a laminated ceramic capacitor, has a small change in electrostatic capacity even under a high temperature condition of 150° C. to 200° C., a change rate in electrostatic capacity within a range of −50.0% to 50.0% (hereinafter, may be described as within ±50.0%) in a temperature range of −55° C. to 200° C., small dielectric losses at 25° C. and 200° C., and further can obtain a insulation resistance value at 200° C. of 40 MΩ or more, and the ceramic electronic components in which the dielectric ceramic composition is used as the dielectric layer can be provided.

