JPH01315904A - Dielectric porcelain and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to high dielectric constant barium titanate porcelain with small temperature changes in dielectric constant (and good signal voltage characteristics) and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Barium titanate ceramic compositions have been widely used as dielectric materials for high-permittivity ceramic capacitors. Among barium titanate-based porcelain compositions, the change in dielectric constant with temperature is small, that is, Y according to the JIS standard.
Materials that satisfy B characteristics and
3-Mn02-Nb2O5 system (JP-A-51-76597
A large number of compositions are known, including the following. Furthermore, in order to meet the recent demands for smaller size and larger capacitance for ceramic multilayer capacitors, dielectric materials with higher dielectric constants and dielectric layers with thinner layers are rapidly progressing. Therefore, there is a growing demand for dielectric materials that have a high dielectric constant, a small temperature change in the dielectric constant (and a small dielectric loss when a high signal voltage is applied).

Problems to be Solved by the Invention In particular, when a ceramic multilayer capacitor having a dielectric layer of 20 μm or less is manufactured using a BaTio3-MnO2-Nb2Os-based ceramic composition with good dielectric constant temperature characteristics, the MnO2 Due to the distribution state of Nb ions in the crystal grains of dielectric ceramic, the dielectric loss exceeds 2.5% when a signal voltage of ]-k H2, 1v is applied. In the present invention, when the dielectric constant is 3000 or less, and the temperature characteristics of the dielectric constant deteriorate depending on the degree of grain growth during firing, the present invention has a dielectric constant of 3000 or more, and the temperature change in the dielectric constant conforms to the JIS standard. To solve the above problems by providing a dielectric porcelain that satisfies the standard YB characteristics and the EIA standard X7R characteristics and has a dielectric loss of 2.5% or less when an AC voltage of 1 kHz and 50 V/mm is applied, and a method for manufacturing the same. It is something.

Means for Solving the Problem BaTiO3 powder with a specific amount of MnO2 or a part of MnO2 replaced with Coo, Nip, ZnO1 and MgO, and a specific amount of Nb2O5
In the dielectric ceramic, the amount of Nb ions dissolved in the center of the crystal grains of the main phase is 0.4 mol % or less. At this time, it is preferable that a phase containing niobium oxide as a main component exists as a secondary phase.

The method for manufacturing the dielectric porcelain described above is such that the primary particle size is 0.1μ.
BaTiO3# powder with a temperature of over 1000℃, 12
Powder heat treated at 50°C or less + B a T i O
Used as the starting material for step 3.

According to the dielectric ceramic of the present invention, Mn in BaTiOs
Since O2 is dissolved in solid solution, the signal voltage characteristics are improved, and the amount of Nb ions dissolved in the center of the main phase crystal grains is zero.
．． Since it is 4 mol % or less, the dielectric constant is high and the temperature characteristics of the dielectric constant are good. In addition, the fact that the secondary phase mainly composed of niobium oxide remains means that the grain growth that occurs after all Nb ions are dissolved in the main phase BaTiO3 crystal is suppressed, and the movement of grain boundaries is suppressed. This means that the uniformity of the composition, especially the uniformity of the distribution of Nb ions, did not occur, which contributes to the improvement of the temperature characteristics of the dielectric constant.

In the method for manufacturing dielectric ceramic of the present invention, heat-treated BaTiO3 powder is used to increase the crystallinity of the main phase, suppress the diffusion of Nb ions into the crystal of the main phase, and improve the crystallinity of the main phase. This is to keep the amount of Nb ions dissolved in the center of the crystal grains to 0.4 mol % or less.

Examples Example 1 This example corresponds to the invention described in Claims 1.2 and 3, and the amount of Nb ions solidly dissolved in the center of the crystal grains of the main phase was 0.4 mol%. The problem is solved by the presence of a phase mainly composed of niobium oxide as a secondary phase.

BaTiO3 powder, particle size 0.0 obtained by hydrothermal method
BaTiO3 fine powder with a diameter of 5 μm and a purity of 99.99% or more was calcined at 1050°C. As a comparative example, BaTiO3 powder obtained by calcining a mixture of BacOs and TiOz with a purity of 99.9% or more at 1050°C (sample N
o, 6), and uncalcined BaCO2 and Ti
Sample No. 7) using a mixture of O2. The above BaTi
For 100 mol parts of O3 powder, N b 2O s is
2.45 mol parts in terms of bO5/2, various amounts of MnO,
C.

Weighed O, Ni01ZnO1 and MgO, and made a 7 m diameter
Mixing was carried out in a ball mill for 17 hours using zirconia cobblestones. Pure water was used as the solvent. 3wtz of polyhinyl alcohol was added as a binder to the powder obtained by drying the solvent, and the mixture was granulated through a 32-mesh nylon sieve and granulated to a diameter of 14 mm under a pressure of 1000 kg/cm2.
, pressure molded to a thickness of 1.2 mm. The obtained disc was held in air at 700°C for 1 hour to burn out the binder component, and then fired in air at 1250 to 1450°C for 2 hours. The temperature at which the density of the obtained sintered body was maximized was set as the optimum firing temperature, and the following electrical properties were measured. Cr-Au was deposited on both sides of the sintered body to form electrodes. dielectric constant, tanδ
under an AC voltage of 1 kHz and IV/mm, -60 to 1
Measurements were made in a temperature range of 30°C. Resistivity is 1kV/mm
It was determined from the value 1 minute after applying the voltage. As a signal voltage characteristic, a signal with a frequency of 1 kHz is
m and then apply a voltage (V2.
5> was measured. In addition, in order to investigate the amount of Nb ions in the center of the crystal grains in the sintered body, we polished the sintered body using an ion mill method to a thickness smaller than the average grain size, and used an energy dispersive fluorescent X-ray microscope with a scanning transmission electron microscope. Composition analysis was performed using a line detection device. The detection limit of Nb ions by this analytical method was 0.4 mol%. Furthermore, the presence or absence of a secondary layer was examined by powder X-ray diffraction.

Table 1 shows the results. 111 in the Nb ion amount column indicates that the amount is below the detection limit of the above analysis method.

(The following is a blank space) As is clear from Table 1, in the N006 sample, 0.9 mol% of Nb ions were present in the center of the crystal grains in the sintered body, and the dielectric constant at room temperature was 2500 or less. Also,
In the absence of a secondary phase, as in the N007 sample, the temperature change in dielectric constant was large. N0 which is the scope of the present invention
The detection limit of the analysis method using the amount of Nb ions dissolved in the center of the crystal grains, as in samples 11 to 5, that is, 0
．． By setting the content to 4 mol% or less and allowing a secondary phase to exist,
The dielectric constant at room temperature was increased to 3000 or more, and the temperature change in the dielectric constant was able to fall within the range of the YB characteristic of the JIS standard and the X7R characteristic of the EIA standard.

FIG. 1 schematically shows the fine structure of the obtained dielectric ceramic. FIG. 1(a) shows a dielectric ceramic according to the scope of the present invention. In the figure, when the center of the main phase 11 was set as the measurement point 12 for the amount of Nb ions, the amount was below the detection limit. A secondary phase 13 mainly composed of Nb oxide exists at the grain boundaries of the main phase, and diffusion of Nb ions due to grain growth is suppressed, and
Since the BaTiO3 used had good crystallinity, the amount of Nb ions present in the center of the crystal grains of the main phase was below the detection limit of measurement. (b) in FIG. 1 is a comparative example, and No.
This corresponds to sample No. 6. There is a secondary phase 13,
Although the grain growth was suppressed, the B a T i used
Due to the poor crystallinity of Os, Nb ions were well diffused to the center 12 of the crystal grains of the main phase 11, resulting in a dielectric constant of 2500 or less. (c) in FIG. 1 is a comparative example, No. 7
This corresponds to a sample of This is an example in which all the added Nb ions diffuse into the crystal grains of the main phase 11, and the Nb ions are uniformly distributed due to grain growth. In all samples, the presence of Nb ions was confirmed around the crystal grains. That is, in the porcelain within the scope of the present invention, there is a large difference in the amount of Nb ion diffusion between the center and the periphery of the crystal grains of the main phase. The problem is solved by limiting the amount of additives, which corresponds to the invention described in section 2.

BaTiOs powder, particle size 0.0 obtained by hydrothermal method
BaTiO3 fine powder with a diameter of 5 μm and a purity of 99.99% or more was calcined at 1050°C. Above B a
For T i O3 powder, various amounts of N b 2O5
, M n 02, Coo, NiO, ZnO1 and Mg
After weighing O, samples were prepared and evaluated in the same manner as in Example 1.

Table 2 shows the results. Further, the area of the additive in the second claim is indicated by diagonal lines.

(Leaving space below) Table 2 Samples marked with # are comparative examples outside the scope of claims Table 2 (Continued) Samples marked with # are comparative examples outside the scope of claims = 15- Samples marked with # are comparative examples outside the scope of claims Comparative examples outside the range Samples marked with # are comparative examples outside the claimed range.As shown above, when the amount of MnO2 is less than 0.4 mol%, the signal voltage is 30. V
/, m m, tan δ exceeds 2.5%, M n
If the sum of O2 and any one of Coo, NiO, ZnO1, and MgO is more than 1.0 mol%, the insulation resistance value will be low (and the capacitance-resistance product will be 500 or less, so it is excluded from the scope of claims). In addition, in the region outside the straight line BC in Fig. 2, the temperature change in the dielectric constant becomes large, and the Nb
If O5/2 was less than 1.8 mol%, the capacitance-resistance product would be low, so it was excluded from the scope of claims.

Example 3 This example corresponds to the invention set forth in claim 4, and solves the problem by limiting the temperature at which the B a T jo 3 fine powder is heat treated.

BaTiO3 with a particle size Q of 05 μm and a purity of 99.99% or more obtained by a hydrothermal method as BaTiO3 powder
Fine powders calcined for 2 hours at various temperatures were used. With respect to 100 mol parts of the above BaTiO3 powder, N b 2
O5 was 2.45 mol parts in terms of NbO5/2, MnO was 0.
．． 54 mole parts were weighed out, and a sample was prepared and evaluated in the same manner as in Example 1.

Table 3 shows the results.

Table 3 As shown, when the calcination temperature of BaTiO3 is 1000°C or less, the crystallinity of BaTiOs particles is low, so during calcination, the diffusion of Nb2O5 into the grains is promoted, and the center of the crystal grains is Nb ions now exist, and the dielectric constant is 2.
It became less than 500. In addition, grain growth during firing is significant, promoting uniformity of composition, and widening temperature changes in dielectric constant (
became. On the other hand, when it is higher than 1250°C, the sintering temperature becomes high, which promotes the diffusion of N b p, Or.
For the same reason, the temperature change in dielectric constant becomes large.

Effects of the Invention According to the dielectric ceramic and its manufacturing method of the present invention, the temperature change in dielectric constant satisfies the YB characteristic of the JIS standard and the X7R characteristic of the EIA standard, and the temperature change is 1 kHz, 50 V/m.
When a signal voltage of m is applied, the dielectric loss is 2.5% or less. Furthermore, it has high resistivity and sufficient mechanical strength, and can be put to practical use as a dielectric material for ceramic capacitors, especially ceramic multilayer capacitors with a dielectric layer thickness of 20 μm or less.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the fine structure of the dielectric ceramic obtained.
Figure 2 shows N b O5/2 and MnO2 or MnO2 added to 100 mol parts of B a T i O3.
This figure shows the sum of Coo, NiO, ZnO1, and MgO.

Claims (4)

[Claims] (1) Nb_2O to 100 mol parts of BaTiO_3
_5 is converted to NbO_5_/_2, x mol%, MnO
When _2 is y mol%, x and y are A shown below,
In the sintered body containing the amount in the range surrounded by B, C, D, and E, the amount of Nb ions dissolved in the center of the crystal grains of the main phase is 0.4 mol% or less. Dielectric porcelain featuring: ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (2) Nb_2O for 100 mol parts of BaTiO_3
_5 converted to NbO_5_/_2 x mol%, CoO
, NiO, ZnO, and MgO, and the total of MnO_2 is y mol%, x and y are amounts in the range surrounded by A, B, C, D, and E shown below, In a sintered body containing 0.38 mol% or more of MnO_2, N is solidly dissolved in the center of the crystal grains of the main phase.
A dielectric ceramic characterized in that the amount of b ions is 0.4 mol% or less. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (3) The amount of Nb ions dissolved in the center of the crystal grains of the main phase is 0.4 mol% or less, and a phase mainly composed of niobium oxide is present as a secondary phase. Dielectric ceramic according to claim 1 or 2. (4) Nb_2O_5 was added to 100 mol parts of BaTiO_3 fine powder with a primary particle size of 0.1 μm or less that was heat-treated at a temperature exceeding 1000°C and below 1250°C.
x mol% in terms of 5_/_2, CoO, NiO, Zn
When the total of at least one of O, MgO, and MnO_2 and MnO_2 is y mol %, x and y are added in amounts within the range surrounded by A, B, C, D, and E shown below. A method for manufacturing dielectric porcelain, which comprises firing. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼