JPS6145850B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic composition for a titanium-based weir layer type semiconductor ceramic capacitor, and in particular, it can be used in any atmosphere firing method such as reducing atmosphere firing, neutral atmosphere firing, as well as oxidizing atmosphere firing including air atmosphere. The present invention provides a ceramic composition for a titanium-based weir layer type semiconductor ceramic capacitor that can be fired and manufactured. When manufacturing barium titanate-based semiconductors, strontium titanate-based semiconductors, etc., which are commonly known semiconductor ceramics, rare earth elements or pentavalent substitution chemicals are added to the above-mentioned main components, except in special cases. In some cases, a semiconductor capacitor is manufactured by firing and manufacturing in a reducing atmosphere or a neutral atmosphere, and in some cases, after obtaining a semiconductor ceramic, it is used as a base material and subjected to a post-treatment to thermally diffuse impurities. There are also examples where it is used. Also, regarding titanium (titanium oxide) based semiconductor porcelain, when titanium oxide (TiO ₂ ) is fired in a reducing atmosphere in the same way as above, as a result of the reducing action, some of the oxygen is released from the TiO ₂ . hand,
It is generally well known that semiconductors are formed by the formation of lower titanium oxide represented by Ti _o O _2o-1 . However, conventional semiconductor porcelain based on TiO ₂ does not have sufficient performance as a semiconductor, and even when manufacturing it, the atmosphere used for firing is limited to a reducing or neutral atmosphere, and these When using an atmosphere, special equipment is required, and there are inherent problems such as the work is time-consuming and difficult to complete.
Furthermore, in order to use this semiconductor porcelain for a capacitor, there arises the problem that the number of steps increases accordingly when performing post-treatments such as thermally diffusing impurities as described above. Therefore, there are no restrictions on the firing atmosphere, and there is no need for processes such as post-processing.
There has been a desire to develop a titanium oxide composition that can provide semiconductor porcelain with good characteristics. The present invention has been made against this background, and its gist is that TiO ₂ is the main component, to which niobium oxide (Nb ₂ O ₅ ) salt is added and blended. The purpose is to manufacture semiconductor porcelain using a composition consisting of This made it possible to obtain semiconductor porcelain with better properties such as tan δ). In this way, if the composition according to the present invention is used,
When manufacturing these titanium-based semiconductor porcelains, unlike the conventional general manufacturing method described above, additives are added.
Nb ₂ O ₅ can effectively act on the reduction of TiO ₂ ,
By effectively promoting the dissociation (elimination) of oxygen from TiO ₂ , it became possible to advantageously produce semiconductor porcelain with excellent performance even in an air atmosphere. There is no longer any need to control the atmosphere inside the furnace. In addition, in the present invention, addition to TiO ₂ ,
The amount of Nb ₂ O ₅ to be blended will be determined appropriately depending on the firing conditions employed and the desired semiconductor performance, but generally it is contained at least 0.01 mol% in the composition. It will be used at the required rate. Further, the upper limit of the amount added is about 23 mol%. Among these, it is noteworthy that particularly excellent semiconductor performance is exhibited at a blending ratio of about 1 to 5 mol % of Nb ₂ O ₅ . In addition, the main component is TiO ₂ as shown above, and this
To the composition in which Nb ₂ O ₅ is added and blended, (1) lanthanum titanate (La ₂ Ti ₂ O ₇ ) is further added as a third component in a proportion less than 5% by weight, or (2) lanthanum dioxide is added. 2% by weight of cerium (CeO ₂ )
(3) Add bismuth oxide (Bi ₂ O ₃ ) in a proportion less than 5% by weight, or combine these methods (1), (2), and (3). By adding two or more kinds of third components, more desirable electrical properties can be imparted to the semiconductor porcelain obtained by firing. That is, one or more of these third components such as La ₂ Ti ₂ O ₇ , CeO ₂ , Bi ₂ O ₃ are added to the TiO ₂ −
By adding Nb ₂ O ₅ to the composition, it is possible to create a semiconductor that exhibits a much higher dielectric constant than conventional titanium-based semiconductor ceramics, has a high areal capacitance, has little change in capacitance with temperature, and has a good loss angle. As a result, porcelain can be obtained, which can be suitably used as a semiconductor capacitor. Examples will be given below to clarify the present invention in more detail; however, the present invention should not be construed as being limited to the description of such examples or the specific explanation above. Without departing from the spirit of the present invention, various changes, modifications, and improvements may be made to the present invention based on the knowledge of those skilled in the art.For example, the raw materials used in the present invention include: In addition to using oxides of each component, it is also possible to use raw materials such as salts of each component that easily become oxides by firing, and it is possible to obtain the same effect by doing so. , it goes without saying. Various TiO ₂ with different blending ratios as shown in Table 1
- Nb ₂ O ₅ composition and various third components (La ₂ Ti ₂ O ₇ , CeO ₂ , BiO ₃ ) added TiO ₂ as shown in Tables 2 to 5 -
A Nb ₂ O ₅ composition was prepared, and after calcination or without calcination, it was formed into a disk shape with a diameter of 16 mm and a thickness of about 0.5 mm according to a general ceramic manufacturing method. , and sintered it at a temperature of 1350°C to 1400°C in an air furnace using a silicon carbide heating element to produce various titanium-based semiconductor ceramics (elements). Next, non-ohmic contact silver electrodes were baked on both sides of the ceramic element thus obtained at a temperature of 800°C to form weir layer type semiconductor porcelain measurement samples. ), the areal capacitance, tan δ, and temperature capacity change rate at -30°C and +85°C (25°C standard) were measured. The obtained results,
They are shown in Tables 1 to 5, respectively. Note that the apparent permittivity in each table is as follows. In other words, one of the dielectric property evaluations of non-semiconductor ceramics is the dielectric constant, and this dielectric constant is proportional to the area of the electrode facing the capacitor, that is, the ceramic, and is dependent on the distance between the electrodes (that is, the thickness of the ceramic). The electrostatic polarization ability unique to ceramics is calculated as the dielectric constant from the actually measured capacitance, which is inversely proportional. However, when semiconductor ceramic is used, an electrode that exhibits a rectifying effect, that is, a weir layer, is used at the contact surface between the electrode and the semiconductor, and the capacitance that appears due to the weir layer is proportional to the electrode area, but the distance between the electrodes,
In other words, since the value is unrelated to the thickness of the semiconductor ceramic, the semiconductor ceramic cannot be expressed as a dielectric constant as seen in the electrostatic polarizability evaluation of non-semiconductor ceramics, but it is correct to express it as an area capacitance, but here, For comparison with non-semiconducting titanium oxide ceramic, the apparent dielectric constant was calculated under the conditions of the same area and the same distance between electrodes, that is, the thickness of the semiconductor ceramic, and the semiconductor ceramic was evaluated.

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[Table] As is clear from the results in Table 1, good semiconductor ceramics based on TiO ₂ were obtained by adding Nb ₂ O ₅ , but especially sample No. 1 (TiO ₂ ; 99.99 mol) %, Nb ₂ O ₅ ; 0.01 mol%) from sample No. 10
(TiO ₂ ; 76.91 _mol %, Nb ₂ O _{5 ;} 2309 mol%). .3 to 6 give the most desirable results. It should be noted that when the amount of Nb ₂ O ₅ added increases, as shown in sample No. 11, it seems that the characteristics of TiO ₂ single porcelain begin to be exhibited again. Also, as is clear from the results in Tables 2 to 5,
For the TiO ₂ -Nb ₂ O ₅ composition, in addition to this
When LaTi ₂ O ₇ , CeO ₂ , Bi ₂ O ₃ are added as third components at various addition ratios (wt%),
Some or all of the properties achieved with the TiO ₂ -Nb ₂ O ₅ composition can be further effectively improved,
In particular, the properties of samples Nos. 3 to 6 were significantly improved. To summarize the results in Tables 2 to 5, compared to the sample consisting of a composition of TiO ₂ and Nb ₂ O ₅ , Bi ₂ O ₃ was added as a third component in an amount greater than 0% by weight and less than 2% by weight. According to the sample results, the dielectric constant is extremely high (40,000 to 190,000), the temperature capacitance change is small (approximately ±10% ±20% in the range of -30℃ to +85℃), and the tanδ is good (3.4 %) and is stable over a wide range. However, although it is not constant depending on the mixing molar ratio of TiO ₂ and Nb ₂ O ₅ , it becomes difficult to convert into a semiconductor as the amount of Bi ₂ O ₃ added approaches 5% by weight. Also,
On the other hand, looking at the effects of CeO ₂ , if the amount added is greater than 0% by weight and less than 0.5% by weight, the change in tan δ and temperature capacity is lower than that of a composition with only Nb ₂ O ₅ added. becomes slightly worse, but
It has the effect of increasing the dielectric constant without being affected much by variations in the TiO ₂ /Nb ₂ O ₅ molar ratio over a wide range.
However, as the amount of CeO ₂ added approaches 2% by weight, it becomes difficult to convert the material into a semiconductor. Furthermore, La ₂ Ti ₂ O ₇
The characteristic of using as the third component is that the amount added is 0.
In the range of more than 2% by weight but less than 2% by weight, the dielectric constant is lower than that of Nb ₂ O ₅ alone, but the temperature capacity change rate, tan δ, is very good as in the case of adding Bi ₂ O ₃ . be. In addition, La ₂ Ti ₂ O ₇
When it approaches 5% by weight, it becomes difficult to make it into a semiconductor.

Claims (1)

[Scope of Claims] 1. A ceramic composition for a titanium-based weir layer type semiconductor ceramic capacitor, which contains titanium oxide as a main component and contains niobium oxide added thereto. 2. The ceramic composition according to claim 1, which contains at least 0.01 mol% of the niobium oxide. 3. A ceramic composition for a titanium-based weir layer type semiconductor ceramic capacitor, which is made of titanium oxide as a main component, to which niobium oxide is added and blended, and further lanthanum titanate is added in an amount of less than 5% by weight. 4. A ceramic composition for a titanium-based weir layer type semiconductor ceramic capacitor, which is made of titanium oxide as a main component, to which niobium oxide is added and blended, and further cerium dioxide is added in an amount of less than 2% by weight. 5. A ceramic composition for a titanium-based weir layer type semiconductor ceramic capacitor, which is made of titanium oxide as a main component, to which niobium oxide is added and blended, and to which bismuth oxide is further added in an amount of less than 5% by weight.