Dielectric ceramic composition and multilayer ceramic electronic component

Abstract

To provide a dielectric ceramic composition capable of yielding a multilayer ceramic electronic component with high reliability while maintaining favorable temperature characteristics.SOLUTION: Provided is a dielectric ceramic composition comprising primary phase particles and particle boundaries existing between the primary phase particles. The primary phase particles contain a perovskite compound as a main component. The perovskite compound includes at least Ca and Sr as A-site elements, and at least Zr and Ti as B-site elements. The dielectric ceramic composition further includes oxides of additive elements. When in the dielectric ceramic composition, the content ratio of the additive elements to 100 pts.mol of the B-site elements is defined as α pts.mol, and in the particle boundaries, the content ratio of the additive elements to 100 pts.mol of the B-site elements is defined as β on an atomic basis, the ratio β / α is between 3.0 and 6.0.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dielectric ceramic composition and a multilayer ceramic electronic component. [Background technology]

[0002] Patent Document 1 describes an invention relating to a reduction-resistant dielectric ceramic composition and a multilayer ceramic capacitor formed by alternately laminating ceramic sheets made of the reduction-resistant dielectric ceramic composition and electrodes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-91588 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to obtain a dielectric ceramic composition that can provide a multilayer ceramic electronic component that has high reliability while maintaining good temperature characteristics. [Means for solving the problem]

[0005] In order to achieve the above object, the dielectric ceramic composition according to the present invention comprises: A dielectric ceramic composition having main phase particles and grain boundaries present between the main phase particles, the main phase particles contain a perovskite compound as a main component, the perovskite compound contains at least Ca and Sr as A-site elements and at least Zr and Ti as B-site elements; The dielectric ceramic composition further contains an oxide of an additive element, In the dielectric ceramic composition, the content ratio of the additive element relative to 100 molar parts of the B-site element is defined as α molar parts, and the content ratio of the additive element relative to 100 molar parts of the B-site element at the grain boundary is defined as β molar parts, and β / α is 3.0 or more and 6.0 or less.

[0006] The content of Ti relative to 100 parts by mole of the B-site element may be 2.0 parts by mole or more and 6.0 parts by mole or less. The additive elements may include at least Si and Al, In the dielectric ceramic composition, the content of Ti may exceed the total content of Si and Al, and the total content of Si and Al may exceed the content of Ti in the grain boundaries.

[0007] The content ratio of Ti relative to 100 molar parts of the B-site elements may be 2.0 molar parts or more and 6.0 molar parts or less, The additive element may include at least one selected from Mn and Cr, In the dielectric ceramic composition, the content of Ti may be greater than the total content of Mn and Cr, and the total content of Mn and Cr may be greater than the content of Ti at the grain boundaries.

[0008] The additive elements may include one or more selected from Mn and Cr, Si, and Al, The total content of the additive elements may be 1.8 molar parts or more and 5.0 molar parts or less relative to 100 molar parts of the B-site elements, In the dielectric ceramic composition, the total content of Mn and Cr may exceed the content of Si, and the content of Si may exceed the total content of Mn and Cr at the grain boundaries.

[0009] The main phase particles may have an average particle size of 0.50 μm or more and 1.20 μm or less.

[0010] A multilayer ceramic electronic component according to the present invention includes any of the above-described dielectric ceramic compositions. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a cross section of a multilayer ceramic capacitor according to one embodiment of the present invention. [Figure 2] FIG. 2 is an HAADF image of a dielectric ceramic composition according to one embodiment of the present invention. [Figure 3] FIG. 3 is a graph showing the results of the line analysis. [Figure 4] FIG. 4 is a graph showing the results of the line analysis. [Figure 5] FIG. 5 is a graph showing the results of the line analysis. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below based on specific embodiments.

[0013] FIG. 1 shows a multilayer ceramic capacitor 1 as an example of a multilayer ceramic electronic component according to this embodiment. The multilayer ceramic capacitor 1 has an element body 10 configured by alternately stacking dielectric layers 2 and internal electrode layers 3. A pair of external electrodes 4 is formed on both ends of the element body 10, and is electrically connected to the internal electrode layers 3 alternately arranged inside the element body 10. There are no particular restrictions on the shape of the element body 10, but it is usually a rectangular parallelepiped. There are also no particular restrictions on the dimensions of the element body 10, and the dimensions may be appropriate depending on the application.

[0014] The dielectric layers 2 are made of the dielectric ceramic composition according to this embodiment, which will be described later. The thickness of each dielectric layer 2 (interlayer thickness) is not particularly limited and can be set as desired depending on the desired characteristics, application, etc. Usually, the interlayer thickness is preferably 100 μm or less, and more preferably 30 μm or less. Furthermore, the number of laminated dielectric layers 2 is not particularly limited, but in this embodiment, it is preferably 20 or more.

[0015] The internal electrode layers 3 are laminated so that their end faces are alternately exposed on the surfaces of two opposing ends of the element body 10 .

[0016] The main component of the conductive material contained in the internal electrode layer 3 is a metal. There are no particular limitations on the metal, and known conductive materials such as Pd, Pd-based alloys, Pt, Pt-based alloys, Ni, Ni-based alloys, Cu, and Cu-based alloys may be used. The metal may contain trace components such as P, S, and Cl, each at about 0.1 mass % or less. The internal electrode layer 3 may be formed using a commercially available electrode paste. The thickness of the internal electrode layer 3 may be determined appropriately depending on the application, etc.

[0017] There are no particular restrictions on the conductive material contained in the external electrodes 4. For example, known conductive materials such as Ni, Cu, Sn, Ag, Pd, Pt, Au, alloys of these, conductive resins, etc. may be used. The thickness of the external electrodes 4 may be determined appropriately depending on the application, etc.

[0018] The method for observing the structure of the dielectric ceramic composition is not particularly limited. For example, a backscattered electron image or an HAADF image of the cross section of the dielectric ceramic composition may be observed. A backscattered electron image can be obtained using, for example, a scanning electron microscope (SEM). An HAADF image can be observed using, for example, a scanning transmission electron microscope (STEM). An HAADF image of the cross section of the dielectric ceramic composition is shown in Figure 2. Note that Figure 2 is the HAADF image of Example 1, which will be described later. Note that in the following description, an HAADF image observed using a STEM may be simply referred to as a STEM image.

[0019] As shown in Fig. 2, the dielectric ceramic composition according to this embodiment has main phase grains 14 and grain boundaries 16 that exist between the main phase grains 14. In a backscattered electron image, the main phase grains 14 can often be recognized as areas with brighter contrast than the grain boundaries 16. This is because the main phase grains 14 often have a higher density than the grain boundaries 16. Therefore, the grain boundaries 16, which often have a lower density than the main phase grains 14, can often be recognized as areas with darker contrast.

[0020] The size of the field of view to be photographed is not particularly limited, but for example, it is about 1 to 50 um square, and the area is 1 to 2500 um. 2 The width of the field of view to be photographed can be selected appropriately depending on the purpose.

[0021] The main phase particles 14 contain a perovskite compound as a main component. The perovskite compound is a compound having a perovskite crystal structure represented by the general formula ABO3 (A is an A-site element, and B is a B-site element).

[0022] The perovskite compound contains at least Ca and Sr as A-site elements, and at least Zr and Ti as B-site elements. It may further contain Ba as an A-site element, and may further contain Hf as a B-site element.

[0023] If only Sr is contained as an A-site element and no Ca is contained, the temperature characteristics and reliability will decrease. If only Ca is contained as an A-site element and no Sr is contained, the insulation characteristics will decrease. If neither Ca nor Sr is contained as an A-site element, the temperature characteristics will decrease and reliability will drop significantly.

[0024] If only Zr is included as a B-site element and no Ti is included, the temperature characteristics will decrease. If only Ti is included as a B-site element and no Zr is included, the temperature characteristics will decrease significantly. If neither Zr nor Ti is included as a B-site element, the temperature characteristics and reliability will decrease.

[0025] The Ca content per 100 molar parts of the A-site elements may be 30 to 90 molar parts, or may be 50 to 80 molar parts. The Sr content per 100 molar parts of the A-site elements may be 10 to 50 molar parts, or may be 20 to 45 molar parts. The Ba content per 100 molar parts of the A-site elements may be 0 to 20 molar parts, or may be 0 to 5.0 molar parts.

[0026] The Zr content relative to 100 molar parts of the B-site elements may be 90 to 99 molar parts, or 94 to 98 molar parts. The Ti content relative to 100 molar parts of the B-site elements may be 0.5 to 8.0 molar parts, or 2.0 to 6.0 molar parts. The Hf content relative to 100 molar parts of the B-site elements may be 0 to 2.0 molar parts. In particular, when the Ti content relative to 100 molar parts of the B-site elements is 2.0 molar parts or more, the sinterability is easily improved. In particular, when the Ti content relative to 100 molar parts of the B-site elements is 6.0 molar parts or less, the content of Ti, which is prone to change in valence, is suppressed, and reliability is easily improved. Furthermore, temperature characteristics are also easily improved.

[0027] The dielectric ceramic composition according to this embodiment further contains an oxide of an additive element in addition to the perovskite compound. There are no particular restrictions on the type of additive element. However, oxygen is not included in the additive elements. In addition, elements that do not combine with oxygen to form an oxide are also not included in the additive elements.

[0028] The additive element may contain one or more selected from Mn and Cr. By containing one or more selected from Mn and Cr, the sinterability is likely to be improved and β / α is likely to be within the range described below, particularly 6.0 or less.

[0029] The additive elements may include Si and Al, or may include one or more selected from Mn and Cr, Si, and Al. The additive elements may include elements other than Mn, Cr, Si, and Al, such as Mg, Li, B, and / or V.

[0030] In the dielectric ceramic composition, the total content ratio of additive elements relative to 100 molar parts of the B-site element content is defined as α molar parts, and in the grain boundary 16, the total content ratio of additive elements relative to 100 molar parts of the B-site element content is defined as β molar parts, and β / α is 3.0 or more and 6.0 or less.

[0031] When β / α is 3.0 or more and 6.0 or less, a relatively large amount of oxides of the additive elements are contained in the grain boundaries 16. In this case, it is thought that the migration of oxygen defects is easily suppressed, thereby enabling high reliability while maintaining good temperature characteristics. When β / α is too small, the grain boundary components (oxides of the additive elements) that inhibit the migration of oxygen defects are likely to decrease, resulting in a decrease in reliability. Both the temperature characteristics and reliability are reduced. When β / α is too large, compounds of the A-site elements and the additive elements are likely to segregate, resulting in a decrease in reliability. Si is relatively easily contained in grain boundaries and has a high sintering effect. Al is relatively easily contained in grain boundaries, and adding it simultaneously with Mn and Si further promotes the sintering effect. Therefore, β / α can be changed by changing the content ratio of Si to Al in the dielectric ceramic composition.

[0032] The content ratio of Ti may exceed the total content ratio of Si and Al in the dielectric ceramic composition, and the total content ratio of Si and Al may exceed the content ratio of Ti in the grain boundary 16. Specifically, the value obtained by subtracting the content ratio of Ti per 100 molar parts of B-site elements in the dielectric ceramic composition by the total content ratio of Si and Al per 100 molar parts of B-site elements may be 0.1 molar parts or more. Furthermore, the value obtained by subtracting the total content ratio of Si and Al per 100 molar parts of B-site elements in the grain boundary 16 by the content ratio of Ti per 100 molar parts of B-site elements may be 0.1 molar parts or more.

[0033] If the Ti content in the dielectric ceramic composition is less than the total content of Si and Al, the excess Si and Al tend to cause segregation of compounds containing A-site elements and Si and / or Al, which tends to reduce reliability.

[0034] If the total content of Si and Al in the grain boundary 16 is equal to or less than the content of Ti, the reliability is likely to decrease because there are few grain boundary components (oxides of the additive elements) that inhibit the movement of oxygen defects.

[0035] The content of Ti relative to 100 molar parts of the B-site elements may be 2.0 parts by 2.0 parts by 6.0 parts by 10 ...

[0036] If the Ti content in the dielectric ceramic composition is less than the total content of Mn and Cr, the excess Mn and / or Cr will easily cause segregation of compounds containing A-site elements and additive elements, which will likely reduce reliability.

[0037] If the total content of Mn and Cr in the grain boundary 16 is equal to or less than the content of Ti, the reliability is likely to decrease because there are few grain boundary components (oxides of the additive elements) that inhibit the movement of oxygen defects.

[0038] In the dielectric ceramic composition, the total content of additive elements relative to 100 molar parts of B-site elements may be 1.8 molar parts or more and 5.0 molar parts or less. Furthermore, the total content of Mn and Cr in the dielectric ceramic composition may be greater than the content of Si, and the content of Si in the grain boundary 16 may be greater than the total content of Mn and Cr. Specifically, in the dielectric ceramic composition, the value obtained by subtracting the total content of Mn and Cr relative to 100 molar parts of B-site elements by the content of Si relative to 100 molar parts of B-site elements may be 0.1 molar parts or more. Furthermore, the value obtained by subtracting the content of Si relative to 100 molar parts of B-site elements by the total content of Mn and Cr relative to 100 molar parts of B-site elements in the grain boundary 16 may be 0.1 molar parts or more.

[0039] If the total content of the additive elements is less than 1.8 parts by mole, the dielectric is difficult to sinter and reliability is likely to decrease, whereas if the total content of the additive elements is more than 5.0 parts by mole, the compounds containing the A-site elements and the additive elements are likely to segregate, resulting in a decrease in reliability.

[0040] If the total content of Mn and Cr in the dielectric ceramic composition is equal to or less than the total content of Si, the dielectric becomes difficult to sinter and reliability tends to decrease. If the content of Si in the grain boundary 16 is equal to or less than the total content of Mn and Cr, the grain boundary components (oxides of additive elements) that inhibit the movement of oxygen defects are small, and reliability tends to decrease.

[0041] There is no particular limitation on the average particle size of the main phase particles 14. For example, it may be 0.20 μm or more and 1.50 μm or less, or 0.50 μm or more and 1.20 μm or less. In particular, reliability is likely to be improved when it is 0.50 μm or more and 1.20 μm or less.

[0042] In the dielectric ceramic composition, the A-site elements, B-site elements, and additive elements are contained in an amount of 99 wt% or more as simple oxides or complex oxides. In Figures 3 to 5 described later, the simple oxides of each element are shown, and these show the amount of the element contained as a simple oxide or complex oxide, converted into the simple oxide.

[0043] The results of a line analysis of the additive element content and the Ti content from left to right along the line 11 drawn in Fig. 2 are shown in Figs. 3 to 5. According to Figs. 2 to 5, the content of each element does not change significantly within the main phase grain 14. In contrast, at the grain boundary 16, the Ti content does not change significantly, but the additive element content (β) increases significantly. Note that since the dielectric ceramic composition shown in Fig. 2 does not contain Cr, the total content of Mn and Cr is equal to the Mn content.

[0044] FIG. 3 shows that in the main phase grains 14, the content of Ti exceeds the total content of Mn and Cr, and at the grain boundaries 16, the total content of Mn and Cr exceeds the content of Ti.

[0045] FIG. 4 shows that in the main phase grains 14, the content of Ti exceeds the total content of Si and Al, and that in the grain boundaries 16, the total content of Si and Al exceeds the content of Ti.

[0046] Fig. 5 shows the magnitude relationship between the content ratio of Mn, the content ratio of Si, and the content ratio of Al. Mn is contained in relatively large amounts in the main phase particles 14, but Si and Al are hardly contained in the main phase particles 14. The same tendency is observed when Mn in the dielectric ceramic composition is replaced with Cr.

[0047] An example of a method for manufacturing the multilayer ceramic capacitor 2 shown in FIG. 1 will now be described.

[0048] First, a description will be given of the manufacturing process of the element body 10. In the manufacturing process of the element body 10, a dielectric paste that becomes the dielectric layer 2 after firing and an internal electrode paste that becomes the internal electrode layer 3 after firing are prepared.

[0049] There are no particular limitations on the method for producing the dielectric paste. For example, it can be produced by the following method. First, raw material powder, mainly of the main phase particles 14 of the dielectric ceramic composition, is prepared. A commercially available perovskite compound powder may be prepared as the raw material powder. Alternatively, the raw material powder may be prepared by preparing an oxide powder of the A-site element and an oxide powder of the B-site element of the perovskite compound, dispersing them in a solvent (e.g., pure water), drying, and performing a heat treatment. There are no particular limitations on the holding temperature in the heat treatment for producing the raw material powder. For example, it may be 900°C or higher and 1300°C or lower. There are no particular limitations on the holding time. For example, it may be 0.5 hours or higher and 5 hours or lower.

[0050] Furthermore, an oxide powder of an additive element may be dispersed in a solvent together with an oxide powder of an A-site element and an oxide powder of a B-site element of a perovskite compound.

[0051] Instead of the oxide powder of each element, a powder of a compound that becomes the oxide of each element upon sintering, such as a powder of a carbonate of each element, or a powder of a composite compound of each element may be used.

[0052] There is no particular restriction on the specific surface area of ​​the raw material powder at this stage, but the specific surface area measured by the BET method must be 3.0 m 2 / g or more 20m 2 / g or less. The larger the specific surface area of ​​the raw material powder, the larger the average particle size of the main phase particles 14 in the finally obtained dielectric ceramic composition tends to be.

[0053] Next, the raw material powder and oxide powder of the additive element (powder of a compound that becomes the oxide of each element upon sintering may be used) may be dispersed in a solvent (e.g., pure water), dried, and heat-treated to prepare a dielectric powder. There is no particular limit to the holding temperature during the heat treatment. For example, it may be 300°C or higher and 700°C or lower. There is no particular limit to the holding time. For example, it may be 0.5 hours or higher and 5 hours or lower. The higher the holding temperature and the longer the holding time in the heat treatment to prepare the dielectric powder, the less additive element will remain at the grain boundaries in the finally obtained dielectric ceramic composition, and the smaller the β / α will tend to be.

[0054] The obtained dielectric powder is then kneaded with a binder and a solvent (organic solvent or water) to prepare a dielectric paste. There are no particular restrictions on the type of binder or solvent. An organic vehicle obtained by mixing a binder and an organic solvent may be used instead of the binder and solvent. The dielectric paste may contain additives such as a plasticizer or a dispersant as needed.

[0055] The internal electrode paste is obtained by kneading the above-mentioned raw materials of the conductive material, a binder, and a solvent (organic solvent or water). There are no particular limitations on the types of binder and solvent. The internal electrode layer paste may contain additives such as co-materials and plasticizers as necessary.

[0056] Using each of the obtained pastes, green sheets and internal electrode patterns are formed, and these are laminated to obtain a green chip.

[0057] The obtained green chip may be subjected to a binder removal process as necessary. The binder removal process may be carried out under known conditions, such as a holding temperature of 180°C or higher and 400°C or lower, and a holding time of 0.5 hours or higher and 24 hours or lower. There are no particular restrictions on the atmosphere during binder removal. In a reducing atmosphere, the holding temperature may be 1100°C or lower.

[0058] After the binder removal process, the green chip is fired to obtain the element body 10. In this embodiment, the firing atmosphere is an oxygen partial pressure of 2.0×10 -13 atm or more 1.0×10 -7 Other firing conditions may be well known, for example, the holding temperature may be 1200°C or higher and 1400°C or lower, and the holding time may be 0.5 hours or higher and 8.0 hours or lower.

[0059] After firing, an annealing treatment may be carried out as necessary. There are no particular restrictions on the conditions for the annealing treatment. For example, the holding temperature may be 500°C or higher and 1150°C or lower, and the holding time may be 0.5 hours or higher and 20 hours or lower. The oxygen partial pressure in the annealing atmosphere may be, for example, 1.0 x 10- 9 atm or above 3.0×10 -5 atm or less.

[0060] The dielectric ceramic composition constituting the dielectric layer 2 of the element body 10 obtained as described above is the dielectric ceramic composition described above. If necessary, the end faces of this element body 10 are polished, and an external electrode paste is applied and baked to form the external electrodes 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like. There are no particular limitations on the method for preparing the external electrode paste, and it may be prepared by the same method as the internal electrode paste.

[0061] In this manner, the multilayer ceramic capacitor 1 according to this embodiment is manufactured.

[0062] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention. [Example]

[0063] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[0064] Experimental Example 1 In Experimental Example 1, the multilayer ceramic capacitor 2 shown in FIG. 1 was fabricated in the following manner.

[0065] First, a dielectric paste was prepared. First, raw material powders of the perovskite compound contained as the main component of the main phase particles (hereinafter sometimes referred to as main component raw material powders) were prepared. Specifically, raw material powders of Ca oxide, Sr oxide, Ba oxide, Zr oxide, and Ti oxide were prepared and weighed so as to obtain the perovskite compounds shown in Table 1. Note that "raw material powders of γ oxide" refers to powders of γ oxide and / or powders of compounds that become γ oxide powders upon heat treatment. Then, each powder was dispersed in pure water, dried, and further heat-treated (holding temperature 1150 to 1250°C, holding time 0.5 to 5 hours) to obtain powders with a specific surface area of ​​3.5 to 20.0 m as measured by the BET method. 2 In Example 6, a main component raw material powder having a specific surface area of ​​about 20 m 2 In Example 7, a main component raw material powder with a specific surface area of ​​about 3.5 m / g was prepared. 2 In the examples and comparative examples other than Examples 6 and 7 in Experimental Example 1, the specific surface area was 5.0 m 2 A main component raw material powder with a molecular weight of about / g was prepared.

[0066] Separately, raw material powders of oxides of additive elements (raw material powder of Mn oxide, raw material powder of Cr oxide, SiO2 powder, and / or Al2O3 powder) were prepared and weighed so that the oxides of each additive element shown in Table 1 were contained in the dielectric ceramic composition. At this time, the order of listing each additive element shown in Table 1 was set to descending order of content based on atomic number.

[0067] The main component raw material powder and the powder of the oxide of the additive element were dispersed in pure water, dried, and then heat-treated to obtain a dielectric powder. The holding temperature was 400°C except for Comparative Example 4, and 1200°C for Comparative Example 4. The holding time was 2.0 hours.

[0068] Dielectric powder and an organic vehicle were kneaded to prepare a dielectric paste. 100 parts by mass of the dielectric powder were mixed with 10 parts by mass of polyvinyl butyral resin, 5 parts by mass of dioctyl phthalate (DOP) as a plasticizer, and 100 parts by mass of alcohol as a solvent in a ball mill to form a paste, thereby obtaining a dielectric layer paste.

[0069] The method for preparing the internal electrode paste is as follows: First, Ni powder, terpineol, ethyl cellulose, and benzotriazole were prepared in a mass ratio of 44.6:52.0:3.0:0.4. These were then kneaded using a three-roll mill to form a paste, thereby preparing the internal electrode paste.

[0070] Next, a green chip was manufactured by the sheet method using the dielectric paste and internal electrode paste. The green chip was then subjected to binder removal, firing, and annealing to obtain a rectangular parallelepiped element body 10 with dimensions of 3.2 mm x 1.6 mm x 0.7 mm. The dimensions are 3.2 mm in the horizontal direction in FIG. 1 and 0.7 mm in the vertical direction (stacking direction) in FIG. 1. The firing temperature was 1200 to 1300°C, the holding time was 2.0 hours, and the firing atmosphere was an oxygen partial pressure of 2.0 x 10 -13 atm or more 1.0×10 -7The reducing atmosphere was set to 1000 MPa or less. In the obtained element body 10, the number of laminated dielectric layers 2 sandwiched between the internal electrode layers 3 was 10, the average thickness of the dielectric layers 2 sandwiched between the internal electrode layers 3 was 5.0 μm, and the average thickness of the internal electrode layers 12 was 1.2 μm.

[0071] Regarding the holding temperature during firing, preliminary tests were carried out for each sample at six holding temperatures: 1200°C, 1220°C, 1240°C, 1260°C, 1280°C, and 1300°C. The lowest holding temperature at which the element body 10 became densified was adopted. Whether the element body 10 became densified or not was confirmed by observing the cross section of the element body 10 with an SEM. Specifically, in the cross section of the element body 10, the area of ​​450 μm was 2 In the above fields of view, it was confirmed whether the area of ​​the voids was 2% or less of the area occupied by the dielectric layer 2 in the field of view. If the element body 10 was not densified at any holding temperature, the holding temperature at which the element body 10 was most densified was adopted. In other words, the holding temperature was set to 1300°C.

[0072] Next, a baked electrode layer containing Cu, a Ni plated layer, and a Sn plated layer were formed in the order listed on the outer surface of the element body 10 to form the external electrodes 4, and the multilayer ceramic capacitor 2 was obtained.

[0073] (Composition of dielectric ceramic composition) Regarding the composition of the dielectric ceramic composition, the dielectric layer 2 was subjected to composition analysis using ICP atomic emission spectroscopy. It was confirmed that the contents of A-site elements, B-site elements, and additive elements were substantially the same between the charged composition and the composition of the dielectric ceramic composition. The composition of the dielectric confirmed by the composition analysis is shown in Tables 1 and 2.

[0074] (Composition of grain boundary 16) The composition of the grain boundary 16, i.e., the content of each additive element in the grain boundary 16, was measured by elemental analysis using STEM-EDS. Specifically, line analysis was performed at five measurement points as shown in Figure 2, and the content of the additive elements at the points included in the grain boundary 16 was averaged. The content of each additive element per 100 molar parts of the B-site component is shown in Table 2. Furthermore, β, which indicates the total content of each additive element, is also shown in Table 2.

[0075] (Average particle size of the main phase particles 14) The average particle size of the main phase particles 14 was measured by observing the cross section of the dielectric layer 2 using an SEM. Specifically, an observation range containing 50 or more main phase particles 14 was set, and the circle-equivalent diameter of each main phase particle 14 was calculated and averaged to measure the average. The circle-equivalent diameter of the main phase particle 14 refers to the diameter of a circle with the same area as the main phase particle 14. The results are shown in Table 2.

[0076] (Temperature characteristics) The temperature characteristics of the multilayer ceramic capacitor 2 were evaluated by measuring the capacitance temperature coefficient τC (unit: ppm / °C). Specifically, a signal with a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms was input to the multilayer ceramic capacitor at 25°C and 125°C, and the capacitance was measured at each temperature range. τC was then calculated from the capacitance C25 at 25°C and the capacitance C125 at 125°C using the following formula. τC={(C125-C25) / C25}×{1 / (125-25)}

[0077] τC was measured for 10 multilayer ceramic capacitors 2, and the average value of τC was calculated. If the average value of τC was between -30 ppm / °C and +30 ppm / °C, it was marked as "passable" in the temperature characteristics column of Table 2. If the average value of τC was less than -30 ppm / °C or more than +30 ppm / °C, it was marked as "unacceptable" in the temperature characteristics column of Table 2.

[0078] (reliability test) The high-temperature accelerated life of the multilayer ceramic capacitor 2 was evaluated. Specifically, the life was measured while maintaining a DC voltage of 800 V (160 V / µm) at 200°C. In this example, the life was determined as the shorter of the time from the start of application until the insulation resistance dropped by one digit or the time from the start of application until the sample failed. In this example, the above evaluation was performed on 20 multilayer ceramic capacitors 2, and the mean time to failure (MTTF) was calculated from the life of each multilayer ceramic capacitor 2. An MTTF of 80.0 hours or more was considered to be good reliability, and an MTTF of 100.0 hours or more was considered to be particularly good reliability. The results are shown in Table 2.

[0079] [Table 1]

[0080] [Table 2]

[0081] As can be seen from Tables 1 and 2, when a perovskite compound having a predetermined composition was contained as the main component, and when additive elements of a predetermined type and content were contained, and when β / α was 3.0 or more and 6.0 or less, both the temperature characteristics and reliability were good.

[0082] In contrast, Comparative Examples 1 and 2, which did not contain Ca as an A-site element, both had insufficient temperature characteristics and reliability. Furthermore, Comparative Example 2, which did not contain either Ca or Sr as an A-site element, had an excessively low β / α ratio, resulting in a significant decrease in reliability.

[0083] In Comparative Example 3, β / α was too high, and reliability was significantly reduced.

[0084] In Comparative Example 4, in which the holding temperature in the heat treatment before the preparation of the dielectric paste was set to 1200° C., the β / α was too low, and the temperature characteristics and reliability were insufficient.

[0085] Experimental Example 2 In Experimental Example 2, the method for producing the multilayer ceramic capacitor 2 was the same as the method for producing Examples 1 to 5 of Experimental Example 1, except for Example 11. In addition, the contents of the A-site elements, B-site elements, and additive elements were changed within predetermined ranges.

[0086] In Example 1, all of the Al2O3 powder and SiO2 powder were mixed with the raw material powder of the oxide of the additive element, whereas in Example 11, a portion of the Al2O3 powder and a portion of the SiO2 powder were mixed with each raw material powder, such as the raw material powder of Ca oxide, to prepare the main component raw material powder. The remaining portions of the Al2O3 powder and the SiO2 powder were then mixed with the raw material powder of the oxide of the additive element. In all other respects, Example 11 was carried out in the same manner as Example 1. The results are shown in Tables 3 and 4.

[0087] [Table 3]

[0088] [Table 4]

[0089] From Tables 3 and 4, it can be seen that when β / α was 3.0 or more and 6.0 or less, both the temperature characteristics and reliability were good. When the content of Ti in the dielectric ceramic composition was 2.0 parts by mol or more and 6.0 parts by mol or less per 100 parts by mol of B-site elements and the content of Ti in the grain boundary was lower than the total content of Si and Al, the reliability was particularly good.

[0090] In contrast, Comparative Examples 6 and 7, which had too low a ratio of β / α, had insufficient temperature characteristics. Furthermore, Comparative Example 6 also had insufficient reliability.

[0091] Experimental Example 3 Example 12 was carried out in the same manner as Example 1, except that the amount of the additive element was increased.

[0092] In Example 13, the B-site elements were varied within a predetermined range.

[0093] Furthermore, in Example 1, the entire amount of the raw material powder of Mn oxide was mixed with the raw material powder of the oxide of the additive element, whereas in Example 13, a portion of the raw material powder of Mn oxide was mixed with each raw material powder, such as the raw material powder of Ca oxide, to prepare the main component raw material powder. The remaining portion of the raw material powder of Mn oxide was then mixed with the raw material powder of the oxide of the additive element. In other respects, Example 13 was carried out in the same manner as Example 1. The results are shown in Tables 5 and 6.

[0094] [Table 5]

[0095] [Table 6]

[0096] As can be seen from Tables 5 and 6, Examples 12 and 13, which contain a perovskite compound having a specified composition as the main component, contain specified types and amounts of additive elements, and have a β / α ratio of 3.0 or more and 6.0 or less, had good temperature characteristics and reliability.

[0097] Example 12, in which the content of Ti in the dielectric ceramic composition was lower than the total content of Mn and Cr, had lower reliability than Example 1. Also, Example 13, in which the content of Ti in the grain boundaries was higher than the total content of Mn and Cr, had lower reliability than Example 1.

[0098] Experimental Example 4 Examples 12 and 14 to 16 were carried out in the same manner as Example 1, except that the ratio of the additive elements added was changed. The results are shown in Tables 5 and 6.

[0099] As can be seen from Tables 5 and 6, Examples 12 and 14 to 16, which contain a perovskite compound having a specified composition as the main component, contain specified types and amounts of additive elements, and have a β / α ratio of 3.0 or more and 6.0 or less, had good temperature characteristics and reliability.

[0100] In the dielectric ceramic composition, Examples 1, 15, and 16, in which the total content of additive elements relative to 100 molar parts of B-site elements was 1.8 molar parts or more and 5.0 molar parts or less, had particularly good reliability. In contrast, in Example 14, in which the total content of additive elements was 1.5 molar parts, sintering did not progress sufficiently compared to Examples 1, 15, and 16, and reliability decreased. In the dielectric ceramic composition, Example 12, in which the total content of additive elements relative to 100 molar parts of B-site elements was 8.0 molar parts, reliability decreased compared to Examples 1, 15, and 16. This is thought to be because a relatively large amount of compounds containing additive elements and A-site elements was generated.

[0101] Experimental Example 5 Example 17 and Comparative Example 8 were carried out under the same conditions as Example 7, except that the proportions of the additive elements and the B-site elements were changed within predetermined ranges. The results are shown in Tables 5 and 6.

[0102] As can be seen from Tables 5 and 6, Example 17, which contains a perovskite compound having a specified composition as the main component, contains specified types and amounts of additive elements, and has a β / α ratio of 3.0 or more and 6.0 or less, had good temperature characteristics and reliability.

[0103] However, in Example 17, the total content of Mn and Cr in the dielectric ceramic composition was lower than the content of Al, so sintering did not progress as well as in Example 7. Furthermore, in Example 17, the content of Si in the grain boundaries was lower than the total content of Mn and Cr, so there were fewer components in the grain boundaries that inhibit the migration of oxygen defects. As a result, Example 17 had lower reliability than Example 7.

[0104] Furthermore, in Comparative Example 8, where β / α was greater than 6.0, the reliability was significantly reduced compared to Example 7.

[0105] Experimental Example 6 In Examples 18 and 19 and Comparative Example 9, the average particle size of the main phase particles 14 was changed by changing the holding temperature during firing compared to Example 7. Specifically, in Comparative Example 9, the holding temperature during firing was lowered by 40°C compared to Example 7, in Example 18, the holding temperature during firing was lowered by 20°C compared to Example 7, and in Example 19, the holding temperature during firing was raised by 20°C compared to Example 7. The results are shown in Tables 7 and 8. Tables 7 and 8 also show the test results of Example 6, in which the average particle size of the main phase particles 14 was changed by changing the specific surface area of ​​the raw material powder.

[0106] [Table 7]

[0107] [Table 8]

[0108] Tables 7 and 8 show that the examples containing a perovskite compound having a predetermined composition as the main component, containing predetermined types and amounts of additive elements, and having a β / α ratio of 3.0 to 6.0 exhibited excellent temperature characteristics and reliability. Furthermore, the examples in which the average particle size of the main phase particles 14 was 0.50 μm to 1.20 μm exhibited particularly improved reliability.

[0109] In contrast, the reliability of Comparative Example 9, in which β / α was too small, was reduced. The reason why β / α in Comparative Example 9 was too small is thought to be that the holding temperature during firing was too low, resulting in insufficient sintering.

[0110] In addition, in Example 6, β / α was 3.0 or more and 6.0 or less, but the average particle size of the main phase particles 14 exceeded 1.20 μm as a result of the additive elements being dissolved in the main phase particles 14. This is thought to have caused an imbalance between the A-site elements and the B-site elements, resulting in lower reliability compared to Examples 7, 18, and 19. [Explanation of symbols]

[0111] 1. Multilayer ceramic capacitors 2. Dielectric Layer 3 Internal electrode layer 4 External electrode 10. Element body 14 Main phase particles 16 grain boundaries

Claims

1. A dielectric ceramic composition having main phase particles and grain boundaries present between the main phase particles, the main phase particles contain a perovskite compound as a main component, the perovskite compound contains at least Ca and Sr as A-site elements and at least Zr and Ti as B-site elements; The dielectric ceramic composition further contains an oxide of an additive element, In the dielectric ceramic composition, the content ratio of the additive element relative to 100 molar parts of the B site element is defined as α molar parts, and the content ratio of the additive element relative to 100 molar parts of the B site element at the grain boundary is defined as β molar parts, and β / α is 3.0 or more and 6.0 or less.

2. the content ratio of Ti relative to 100 molar parts of the B-site elements is 2.0 molar parts or more and 6.0 molar parts or less, The additive elements include at least Si and Al, 2. The dielectric ceramic composition according to claim 1, wherein the content of Ti in said dielectric ceramic composition exceeds the total content of Si and Al, and the total content of Si and Al in said grain boundaries exceeds the content of Ti.

3. the content ratio of Ti relative to 100 molar parts of the B-site elements is 2.0 molar parts or more and 6.0 molar parts or less, The additive element contains at least one selected from Mn and Cr, 2. The dielectric ceramic composition according to claim 1, wherein the content of Ti in said dielectric ceramic composition exceeds the total content of Mn and Cr, and the total content of Mn and Cr in said grain boundaries exceeds the content of Ti.

4. The additive elements include one or more selected from Mn and Cr, Si, and Al, the total content of the additive elements is 1.8 molar parts or more and 5.0 molar parts or less relative to 100 molar parts of the B-site elements, 2. The dielectric ceramic composition according to claim 1, wherein the total content of Mn and Cr in said dielectric ceramic composition exceeds the content of Si, and the content of Si in said grain boundaries exceeds the total content of Mn and Cr.

5. 5. The dielectric ceramic composition according to claim 1, wherein the average particle size of the main phase particles is 0.50 μm or more and 1.20 μm or less.

6. A multilayer ceramic electronic component comprising the dielectric ceramic composition according to any one of claims 1 to 4.

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