JPH0752695B2 - Semiconductor porcelain material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor ceramic material having a dielectric layer provided at a grain boundary of the semiconductor ceramic.

[Prior Art] In recent years, a grain boundary dielectric type semiconductor ceramic capacitor in which a high insulating layer is provided as a dielectric at a grain boundary of a semiconductor ceramic mainly composed of strontium titanate (SrTiO ₃ ) has been widely used. In this semiconductor porcelain material, strontium titanate (SrTiO ₃ ) is used as a main material, and niobium oxide (Nb ₂ O ₅ ) and yttrium oxide (Y ₂ O ₃ ) are added as valence control agents to the material. Silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ) etc. are added as a sintering aid and sintered in a neutral or reducing atmosphere to obtain a semiconductor porcelain. Manganese oxide (MnO ₂ ), copper oxide (CuO), bismuth oxide (Bi
It was obtained by thermally diffusing a metal oxide such as ₂ O ₃ ) as the diffusing substance (Japanese Patent Publication No. 58-27649 and Japanese Patent Laid-Open No. 52-9).
8997 publication).

[Problems to be Solved by the Invention] Depending on what kind of material is used as the diffusing material, the electrical characteristics of the obtained semiconductor ceramic material [relative permittivity (ε _A ), dielectric loss tangent (tan δ), volume resistivity (Ρ) etc.]
There is a difference. For example, a semiconductor ceramic material obtained by using manganese oxide (MnO ₂ ) or copper oxide (CuO) as a diffusing material has a high volume resistivity but a high dielectric loss tangent and a low relative dielectric constant. On the other hand, when bismuth oxide (Bi ₂ O ₃ ) is used as the diffusing substance, the dielectric loss tangent is low and the relative dielectric constant is high, but the volume resistivity is low. Further, when a mixture of bismuth oxide (Bi ₂ O ₃₎ and copper oxide (CuO) as the diffusion material, bismuth oxide (Bi ₂
Although each electrical characteristic is improved on average as compared with the case where O ₃ ) or copper oxide (CuO) is used alone, it cannot be said that sufficient characteristic values are achieved. Thus, a semiconductor ceramic material having good results (high relative permittivity and volume resistivity and low dielectric loss tangent) for all electrical characteristics has not yet been obtained.

The present inventor has investigated the electrical characteristics of semiconductor porcelain substances using various materials as diffusion substances, and as a result, bismuth oxide (Bi ₂ O ₃ ), copper oxide (CuO) It has been found that when a mixture with sodium (Na ₂ CO ₃ ) or sodium oxide (Na ₂ O) is used, a semiconductor porcelain material having good electrical characteristics can be obtained.

The present invention has been made based on such findings, and an object of the present invention is to provide a semiconductor porcelain material that can obtain good results with respect to all the above-mentioned electrical characteristics.

[Means for solving problems]

The semiconductor porcelain material according to the present invention contains bismuth oxide (Bi) at a crystal grain boundary of a semiconductor porcelain containing strontium titanate containing 0.1 to 2 mol% of niobium oxide and silicon oxide, respectively.
20-98 mol% of ₂ O ₃ ) and 1-30 mol% of copper oxide (CuO)
And sodium carbonate (Na ₂ CO ₃ ) or sodium oxide (Na
₂ O) of 1 to 70 mol% is diffused, a dielectric layer is formed at the crystal grain boundaries, and the relative dielectric constant is 120,000 or more,
The volume resistivity is 1.5 × 10 ¹⁰ Ω-cm or more.

[Action]

Since semiconductor porcelain contains 0.1 to 2 mol% of silicon oxide, the quality and characteristics of the product are stable, and 1 to 70 mol% of sodium carbonate is contained as a diffusing substance, so that the relative dielectric constant is 120,000 or more, 1.5 × 10 5. Each volume resistivity of ¹⁰ Ω-cm or more can be set, and the obtained semiconductor porcelain material has a significantly improved relative dielectric constant and volume resistivity. Moreover, the dielectric loss tangent is sufficiently low.

〔Example〕

Hereinafter, examples in which the present invention is applied to, for example, manufacturing of capacitors will be specifically described.

First, a method for manufacturing a semiconductor ceramic material of the present invention will be described. For example, strontium titanate (SrTiO ₃ ) is mixed with niobium oxide (Nb ₂ O ₅ ) and silicon oxide (SiO ₂ ) in an amount of 0.1 to ₂ respectively.
After adding in the range of mol% and mixing well, diameter 10mm,
It is pressed into a disk with a thickness of 0.8 mm. After this, hydrogen 1 to 1
A semiconductor porcelain is manufactured by firing at 1420 to 1520 ° C. for 2 to 4 hours in an atmosphere consisting of 5% and 99 to 85% nitrogen. Next, diffusion material (bismuth oxide (Bi ₂ O
₃ ), copper oxide (CuO), and sodium carbonate (Na ₂ CO ₃ ) mixture), and heated at 1000 to 1300 ° C. for 1 to 2 hours to thermally diffuse the diffusion material. Finally, print the silver paste on both sides of the semiconductor porcelain material thus obtained,
The silver electrode is baked by about a degree to obtain a capacitor.

The electrical characteristics of the semiconductor porcelain material obtained by applying the mixture of bismuth oxide (Bi ₂ O ₃ ), copper oxide (CuO) and sodium carbonate (Na ₂ CO ₃ ) to the semiconductor porcelain at various composition ratios are shown below. First
Shown in the table. Those marked with * in the leftmost column in the table are
It shows that the composition ratio of the mixture deviates from the conditions of the present invention. Further, the relative permittivity (ε _A ) and the dielectric loss tangent (tan δ) in the table are values measured at a frequency of 1 kHz and a voltage of 1 V, and the volume resistivity (ρ) is a value obtained by a DC50V one-minute value.

From Table 1, the composition ratio of the mixture satisfies the conditions of the present invention, that is, 20 to 98 mol% of bismuth oxide (Bi ₂ O ₃ ), 1 to 3 mol% of copper oxide (CuO), and sodium carbonate. (Na ₂
It can be seen that those satisfying the condition of CO ₃ ) 1 to 70 mol% have good electrical characteristics. When the bismuth oxide (Bi ₂ O ₃ ) content is less than 20 mol%, or when it is 9%,
It can also be seen that when it exceeds 8 mol%, the relative permittivity and the resistivity decrease. It can also be seen that when the copper oxide (CuO) content is less than 1 mol%, the resistivity is insufficient, and when it exceeds 30 mol%, the relative dielectric constant decreases and the dielectric loss tangent deteriorates. Sodium carbonate (Na ₂ CO ₃ ) is 1
It can also be seen that when it is less than mol%, the relative dielectric constant decreases, and when it exceeds 70 mol%, the dielectric loss tangent deteriorates and the volume resistance decreases.

Further, from Table 1, 45 mol% of bismuth oxide (Bi ₂ O ₃ ),
Copper oxide (CuO) 10 mol%, sodium carbonate (Na ₂ CO ₃ ) 45
The example of the present invention using a mixture of mol% as a diffusing substance has a relative dielectric constant of 1.4 times and a volume resistivity of 8.1 times as compared with a conventional example using a simple substance of bismuth oxide (Bi ₂ O ₃ ). It can also be seen that the electrical characteristics are remarkably improved.

Further, the semiconductor porcelain material of the present invention as described above has an advantage that it can be obtained by a simple manufacturing process of coating a diffusion material and firing in the air.

In addition, in the above-mentioned examples, it was decided to apply a mixture of bismuth oxide (Bi ₂ O ₃ ), copper oxide (CuO), and sodium carbonate (Na ₂ CO ₃ ) as a diffusion material on one surface of the semiconductor porcelain. , Bismuth oxide (Bi ₂ O ₃ ) 20-9 instead of the mixture
Even if a mixture of 8 mol%, copper oxide (CuO) 1 to 30 mol% and sodium oxide (Na ₂ O) 1 to 70 mol% is applied, the electrical characteristics are similar to those of the conventional example, as in the above-described embodiment. And improve.

Further, in the above-mentioned embodiment, the silver paste is printed on both sides of the semiconductor porcelain and baked to form a silver electrode, but it goes without saying that other known electrode materials may be used. Further, the firing atmosphere at the time of manufacturing the semiconductor porcelain is not limited to the atmosphere composed of 1 to 15% hydrogen and 99 to 85% nitrogen as in the above-mentioned embodiment, as long as the sample can be sufficiently semiconducting. It goes without saying that other atmospheres are acceptable.

〔effect〕

As described above, in the semiconductor porcelain material according to the present invention,
Since semiconductor porcelain contains 0.1 to 2 mol% of silicon oxide and 1 to 70 mol% of sodium carbonate as a diffusing substance, the quality and characteristics of the product are stable when used as a capacitor, etc. Relative permittivity above 1.5
The volume resistivity of × 10 ¹⁰ Ω-cm or more can be easily set. In addition, good results can be obtained at the same time with respect to electrical characteristics such as relative permittivity, dielectric loss tangent, and volume resistivity. The present invention exhibits excellent effects such as being applicable to a wide range of stars, thermistors and the like.

Front page continued (72) Inventor Osamu Kanda 1-3-3 Nishi-Nagasumotodori, Amagasaki City, Hyogo Prefecture Sumitomo Metal Industries, Ltd. Research Institute (72) Inventor Kyuji Shibata Nishinagasumoto-dori, Amagasaki City, Hyogo Prefecture 3-chome, Sumitomo Metal Industries, Ltd. (56) References JP-A-57-123863 (JP, A) JP-A-59-127826 (JP, A)

Claims (1)

[Claims] 1. Bismuth oxide (Bi ₂ O ₃ ) is contained in an amount of 20 to 98 mol% at a crystal grain boundary of a semiconductor ceramic containing strontium titanate containing 0.1 to 2 mol% of niobium oxide and silicon oxide, respectively.
And 1 to 30 mol% of copper oxide (CuO) and 1 to 70 mol% of sodium carbonate (Na ₂ CO ₃ ) or sodium oxide (Na ₂ O)
The composition consisting of and diffuses, a dielectric layer is formed at the crystal grain boundary, the relative dielectric constant is 120,000 or more, and the volume resistivity is 1.
A semiconductor porcelain material characterized by having a value of 5 × 10 ¹⁰ Ω-cm or more.