JPH04260660A - Production of irreducible dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a process for producing an irreducible dielectric ceramic composition capable of forming a small-sized highly reliable laminated ceramic capacitor. CONSTITUTION:An irreversible dielectric ceramic composition having a perovskite structure expressed by the general formula (A1-xRx)yMO3 is produced by precipitating carbonates or hydroxides of the constituent elements from aqueous solution of the inorganic salts of the elements and subjecting the precipitate to filtration, washing with water, drying, calcination and crushing. In the above formula, A is at least one kind of element selected from Ba, Sr, Ca and Mg; R is at least one kind of rare-earth element; and M is at least one kind of element selected from Ti, Zr and Sn.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-reducible dielectric ceramic composition, and more particularly to a method for producing a non-reducible dielectric ceramic composition used as a material for laminated ceramic capacitors and the like.

0002

2. Description of the Related Art When manufacturing a multilayer ceramic capacitor, a sheet-like dielectric material and an electrode material to be an internal electrode are laminated and integrated by thermocompression bonding to obtain a laminated body. This laminate is fired in a predetermined atmosphere to form dielectric ceramic. Then, on the end face of this dielectric porcelain,
A multilayer ceramic capacitor is manufactured by baking an external electrode that is electrically connected to an internal electrode.

The dielectric ceramic composition used in such multilayer ceramic capacitors has the property that when fired under neutral or reducing low oxygen partial pressure, it is reduced and becomes a semiconductor. Therefore, when such a dielectric material is used as a material for a multilayer ceramic capacitor, the internal electrode material must be a high oxygen content material that does not melt at the sintering temperature of the dielectric ceramic material and does not convert the dielectric ceramic material into a semiconductor. It was necessary to use noble metals such as palladium and platinum, which do not oxidize even when fired under pressure. As described above, since an expensive material must be used as the internal electrode material, the manufacturing cost of the multilayer capacitor increases. In particular, in recent years, the miniaturization of electronic components has progressed rapidly, and the trend toward miniaturization and increased capacity of multilayer ceramic capacitors has become noticeable. Therefore, the proportion of electrode material costs in the manufacturing cost of multilayer ceramic capacitors is increasing.

[0004] In order to solve this problem, it is conceivable to use an inexpensive base metal such as nickel as the internal electrode material. However, when such base metals are used as internal electrode materials and fired under conventional conditions, the electrode materials become oxidized and do not function as electrodes. In order to use such a base metal as an electrode material, it must not turn into a semiconductor even when fired in a neutral or reducing atmosphere with a low oxygen partial pressure, and must have sufficient resistivity and excellent properties as a dielectric material for capacitors. What is needed is a dielectric porcelain material that has improved dielectric properties. Examples of materials that meet these conditions include barium titanate solid solutions containing rare earth elements such as Ce, as disclosed in Japanese Patent Publication No. 02-063664. Such a material is a very useful composition because it is not reduced even when fired in a reducing atmosphere, has a small grain size, and exhibits a high dielectric constant.

[0005] As a method for obtaining such a non-reducible dielectric ceramic composition, there is a method of mixing and calcining raw materials consisting of carbonates and oxides to synthesize them.

[0006]

[Problems to be Solved by the Invention] However, with such conventional methods, it is difficult to reduce the raw material itself to 1 μm or less, and therefore it is difficult to obtain a uniform composition even if the raw material is calcined. difficult. When a barium titanate solid solution containing a rare earth element such as Ce is produced by such a method as a non-reducible dielectric ceramic composition, the rare earth element does not diffuse uniformly after calcination, resulting in variations in concentration. When a sintered body is made using this raw material, it is clear that reliability is low when made into a multilayer capacitor in areas with high concentrations of rare earth elements, probably because the non-reducible barium titanate solid solution partially becomes a semiconductor. Became.

Therefore, the main object of the present invention is to obtain a highly reliable multilayer capacitor when producing a multilayer capacitor in the case of obtaining a non-reducible dielectric ceramic composition containing a rare earth element. An object of the present invention is to provide a method for producing a non-reducible dielectric ceramic composition.

[0008]

[Means for Solving the Problems] The method of the present invention is based on Ba
, Sr, Ca, Mg, at least one selected from rare earth elements is R, and at least one selected from Ti, Zr, Sn is M, then the following general Formula (A1-x Rx )y M
O3, and x and y are 0.001≦x≦0.
020, a method for producing a perovskite-type non-reducible dielectric ceramic composition satisfying the relationship of 1.002≦y≦1.03, wherein carbonate salts are obtained from an aqueous solution of a mixture of water-soluble inorganic salts of each component. At least one type of precipitate is prepared as a precipitate or a precipitate as a hydroxide, and a slurry containing each precipitate is mixed, filtered, washed with water, dried, calcined, and pulverized. This is a method for producing a dielectric ceramic composition.

[0009] Another method of the present invention is that Ba, Sr
, Ca, Mg at least one selected from A,
At least one selected from rare earth elements R, T
When at least one type selected from i, Zr, and Sn is M, the following general formula (A1-x Rx )y MO3
, where x and y are 0.001≦x≦0.020
, 1.002≦y≦1.03. A method for producing a perovskite non-reducible dielectric ceramic composition satisfying the relationship of , 1.002≦y≦1.03. This is a method for producing a non-reducible dielectric ceramic composition, in which a precipitate is prepared by sequentially precipitating oxides, and the precipitate is filtered, washed with water, dried, calcined, and crushed.

0010

[Operation] The precipitate of carbonate or hydroxide obtained from an aqueous solution of a water-soluble inorganic salt has a small particle size of about 0.01 μm in diameter. Therefore, each element is well dispersed,
Rare earth elements are also uniformly dispersed.

Here, the general formula (A1-x Rx )y
The reason for limiting x and y of the non-reducible dielectric ceramic composition represented by MO3 will be explained. In other words, x is 0
．． If it is smaller than 001, no reliability improvement effect is observed, which is not preferable. Moreover, when x exceeds 0.02, reliability decreases, which is not preferable. y is 1.002
If it is smaller, it is undesirable because it is more likely to be made into a semiconductor and the reliability will be significantly lowered. Moreover, when y exceeds 1.03, sinterability deteriorates, which is not preferable.

0012

According to the present invention, a composition in which each element and rare earth element are uniformly dispersed can be obtained, so that a highly reliable multilayer ceramic capacitor can be obtained when a multilayer ceramic capacitor is manufactured. Therefore,
Compared to multilayer ceramic capacitors using conventional dielectric ceramic compositions, the thickness of the ceramic element portion between internal electrodes can be significantly reduced. Therefore, it is possible to make the multilayer ceramic capacitor smaller and larger in capacity. Further, since this non-reducible dielectric ceramic composition is non-reducible, base metals can be used as the internal electrode material, and manufacturing costs can be lowered compared to those using noble metals.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments.

[0014]

[Example] First, at least one inorganic salt selected from Ba, Sr, Ca, and Mg, at least one inorganic salt selected from rare earth elements, and at least one selected from Ti, Zr, and Sn. One type of inorganic salt is prepared. All of these inorganic salts are water-soluble. Examples of water-soluble inorganic salts include nitrates, chlorides, iodides, bromides, and carboxylates. By mixing these aqueous solutions and adding soda carbonate or the like, a precipitate that precipitates as carbonate is obtained. Alternatively, by mixing each aqueous solution and adding caustic soda or the like, a precipitate that precipitates as hydroxide can be obtained. These precipitates are 0.01μ
It has a small particle size of around m. Whether the precipitate is to be precipitated as a carbonate or a hydroxide is determined from the viewpoint of stable precipitation. A slurry is obtained using these precipitates.

Alternatively, a slurry may be obtained by sequentially adding sodium carbonate and caustic soda to an aqueous solution of an inorganic salt to precipitate the carbonate and hydroxide. In this case as well, 0.0
It has a small particle size of around 1 μm. Therefore, in the obtained slurry, each element is well dispersed, and in particular, rare earth elements are also uniformly dispersed. By filtering, washing, drying, calcining, and pulverizing this slurry, a non-reducible dielectric ceramic material in which rare earth elements are uniformly dissolved in a perovskite structure can be obtained.

[0016] When this non-reducible dielectric ceramic material is analyzed with an X-ray microanalyzer, it is found that it is similar to that seen in calcined raw materials obtained by conventional solid-phase sintering methods in which oxides and carbonates are crushed and mixed. No aggregates of unreacted rare earth element oxides or aggregates of A-site element oxides or B-site element oxides forming a perovskite structure were observed. In addition, when this non-reducible dielectric ceramic material is used to process a chip for a multilayer capacitor and this is fired in a reducing atmosphere, when raw materials obtained by conventional solid-phase sintering methods are used, There is no occurrence of a secondary layer that causes a decrease in reliability, as was seen in the previous study.

Therefore, in a multilayer ceramic capacitor using a non-reducible dielectric ceramic composition according to the method of the present invention, a conventional non-reducible barium titanate solid solution or a non-reducible barium titanate solid solution containing a rare earth element is used. Reliability in insulation resistance is improved by more than one order of magnitude compared to conventional products. Note that SiO2, which is used as a normal ceramic technology,
Mineralizers such as MnO and Cr to increase insulation resistance.
Even if appropriate amounts of 2 O3, Fe2 O3, etc. are added, the effects of the present invention will not be impaired.

As an example, raw materials were first prepared in the proportions shown in Table 1. Then, in the first tank, BaCl2
, SrCl2 , MgCl2 , and CeCl2 , the pH was adjusted by adding sodium carbonate (Na2 CO3 ), and BaCO3 , SrCO3 , MgCO
3, Ce2 (CO3)2. In addition, in the second tank, TiCl4, ZrOCl2
・Mix each aqueous solution of 8H2O, add 30% hydrogen peroxide as a stabilizer, and add caustic soda (NaO
The pH was adjusted by adding H) to obtain a precipitate containing Ti and Zr. Furthermore, each precipitate slurry is thoroughly and uniformly mixed,
Washing and dehydration were repeated. The washed and dehydrated slurry was dried at 110°C to obtain a dry raw material. After that, the dry raw materials were calcined at a temperature of 1100°C for 2 hours, and (Ba, Sr
, Mg, Ce) (Ti, Zr) O3 based calcined powder I was obtained.

[0019]

[Table 1]

Next, raw materials were prepared in the proportions shown in Table 2. Then, in the first tank, Ba(NO3)2, C
a Mix each aqueous solution of (NO3)2.4H2O, add soda carbonate (Na2CO3) to adjust the pH,
It was precipitated as BaCO3 and CaCO3. Also,
In the second tank, NdCl2 ・6H2 O, TiC
14, ZrOCl2 ・8H2 O, and SnCl4 aqueous solutions were mixed, 30% hydrogen peroxide solution as a stabilizer was added to this, and caustic soda (NaOH) was added to p
H was adjusted to obtain a precipitate containing Nd, Ti, Zr, and Sn. Furthermore, each precipitate slurry was thoroughly and uniformly mixed, and washing and dehydration were repeated. The washed and dehydrated slurry was dried at 110°C to obtain a dry raw material. After that, the dry raw materials were calcined at a temperature of 1150°C for 2 hours (Ba, Ca,
Nd) (Ti, Zr, Sn) O3 based calcined powder II was obtained.

[0021]

[Table 2]

[0022] Raw materials were also prepared in the proportions shown in Table 3. Then, in the first tank, Ba(CH3COO)2
, Sr(NO3)2, and CaCl2 were mixed, and sodium carbonate (Na2 CO3) was added to adjust the pH.
BaCO3, SrCO3, CaCO3
It was precipitated as In addition, in the second tank, DyCl
3, TiCl4, SnCl4, Sm(NO3)
3. Mix each aqueous solution of 6H2O, add 30% hydrogen peroxide solution as a stabilizer, and add caustic soda (N
aOH) was added to adjust the pH, and a precipitate containing Dy, Ti, and Sn was obtained. Furthermore, each precipitate slurry was thoroughly and uniformly mixed, and washing and dehydration were repeated. The washed and dehydrated slurry was dried at 110°C to obtain a dry raw material. After that, the dry raw materials were calcined at a temperature of 1200℃ for 2 hours.
Ba, Sr, Ca, Dy, Sm) (Ti, Sn) O3
A calcined powder III of the system was obtained.

[0023]

[Table 3]

Furthermore, raw materials having a purity of 99.8% or more were prepared in the proportions shown in Table 4. This raw material was put into a ball mill together with 3000 cc of pure water, and pulverized and mixed for 16 hours using 5000 g of zirconia crushed boulders with a diameter of 5 mm to obtain a mixture. This mixture was calcined at a temperature of 1180°C, and the conventional solid phase method (Ba, Sr, Mg,
A Ce)(Ti,Zr)O3 based calcined powder IV was obtained.

[0025]

[Table 4]

[0026] 200 g of calcined powder I was placed in a resin pot with an appropriate amount of organic solvent and organic binder, and
Using 2000 g of millimeter zirconia crushing stones,
The mixture was mixed for 10 hours to obtain a slurry. Similarly, using calcined powder II, calcined powder III and calcined powder IV,
Got slurry.

[0027] Using each of the obtained slurries, a 15 μm thick film was cast by a casting method using a doctor blade.
A ceramic green sheet of m was produced. On this ceramic green sheet, a paste for internal electrodes using Ni powder was screen printed using a conventional method for manufacturing multilayer ceramic capacitors. Ceramic green sheets printed with paste for internal electrodes were stacked so that the number of layers was 10, and they were integrated by hot pressing to obtain a laminate. Thereafter, this laminate was cut into predetermined dimensions to produce green chips.

The obtained raw chips were held for 2 hours in an atmosphere with a temperature of 300° C. and an oxygen partial pressure of 100 ppm to perform a binder removal treatment. The raw chips subjected to the binder removal treatment were fired at 1250 to 1300°C for 2 hours in a reducing atmosphere adjusted to an oxygen partial pressure of 3 x 10-8 to 3 x 10-10 atm to obtain a sintered body. . This sintered body was attached with an external electrode and used as a sample. Note that the sample produced using calcined powder I was referred to as sample I. Similarly, calcined powder II, III, I
The samples using V were designated as samples II, III, and IV, respectively.

[0029] Regarding the obtained samples I, II, III, and IV, the capacitance, dielectric constant (ε), dielectric loss (tan δ)
, measure insulation resistance and mean time to failure (MTTF),
It is shown in Table 5. Note that the capacitance and dielectric loss are 1k
The measurement was performed by applying an alternating current voltage of Hz, 1 Vrms. Further, the dielectric constant was calculated from the capacitance by measuring the electrode area and the distance between the electrodes. Furthermore, the mean failure time is a value measured under the condition of applying a DC electric field of 64 V/10 μm in an atmosphere of 150° C. Also,
Regarding insulation resistance, its logarithm value (logIR) is shown.

[0030]

[Table 5]

[0031] As can be seen from Table 5, in sample IV consisting only of calcined powder obtained by the conventional solid phase sintering method,
The mean failure time is short at 1.3 hours, and the reliability is poor. On the other hand, sample I consisting of a ceramic composition manufactured by using a non-reducible dielectric ceramic composition manufactured by the method of the present invention
, II, and III are 30.3 to 44.5 hours, and it can be confirmed that the average time to failure is 30.3 to 44.5 hours, which is one order of magnitude better than that of sample IV.

Claims (2)

[Claims] [Claim 1] At least one selected from Ba, Sr, Ca, and Mg is A, at least one selected from rare earth elements is R, and at least one selected from Ti, Zr, and Sn is M. Then, the following general formula (A1
-xRx)yMO3, where x and y satisfy the following relationships: 0.001≦x≦0.020 1.002≦y≦1.03 Production of a perovskite-type non-reducible dielectric ceramic composition A method, comprising: preparing at least one kind of precipitate as a carbonate or a precipitate as a hydroxide from an aqueous solution of a mixture of water-soluble inorganic salts of each component; A method for producing a non-reducible dielectric ceramic composition, which involves mixing a slurry containing a substance, filtering it, washing it with water, drying it, calcining it, and crushing it. [Claim 2] At least one selected from Ba, Sr, Ca, and Mg is A, at least one selected from rare earth elements is R, and at least one selected from Ti, Zr, and Sn is M. Then, the following general formula (A1
-xRx)yMO3, where x and y satisfy the following relationships: 0.001≦x≦0.020 1.002≦y≦1.03 Production of a perovskite-type non-reducible dielectric ceramic composition The method comprises sequentially precipitating carbonates and hydroxides from an aqueous solution containing water-soluble inorganic salts of each component to prepare a precipitate, and filtering, washing, drying, calcining, and pulverizing the precipitate. A method for producing a non-reducible dielectric ceramic composition.