JPH0310217B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a nonlinear ceramic capacitor made of a dielectric ceramic composition containing barium titanate as a main component.
It is characterized by generating high voltage pulses. BACKGROUND ART Conventionally, pulse generators having a structure consisting of an inductive element and a nonlinear capacitor having a perovskite structure have been known. It is known that polycrystalline solid solutions such as barium titanate and lead titanate are effective for this perovskite dielectric element. However, high pulse voltage cannot be obtained with good reproducibility. Furthermore, it has the drawbacks of large variations in pulse voltage, and also has fatal drawbacks such as a sudden drop in pulse voltage when the temperature is slightly higher than room temperature, which poses a practical problem. The present invention provides a nonlinear ceramic capacitor that has high pulse voltage with good reproducibility, has little variation in pulse voltage, and has high pulse voltage over a wide temperature range. That is, we have discovered that by incorporating zirconium into a barium titanate solid solution having a perovskite crystal structure, a nonlinear ceramic capacitor that generates a high pulse voltage over a wide temperature range can be obtained with good reproducibility. Hereinafter, the present invention will be explained in detail based on examples. Example 1 BaCO ₃ , TiO ₂ , ZrO ₂ , and SnO ₂ as starting materials were weighed to have the composition shown in Table 1, and wet mixed with water and agate cobbles in a polyethylene pot for about 16 hours.
A prepared raw material was obtained by filtering and drying. This was calcined at 1,120℃ for 2 hours, and then crushed in a polyethylene pot with water and agate cobbles for about 16 hours, and
Approximately 3.0% organic binder is added to the dried raw materials to form granules, which are then molded into a disk shape with a diameter of 16.0 mmφ and a thickness of 0.65 mm under a pressure of 1 ton/cm ² . Next, a 12.0 mmφ silver electrode was applied to the porcelain obtained by firing it at 1400°C for about 2 hours, and it was baked at 800°C for 30 minutes to obtain an element for a nonlinear ceramic capacitor.
The electrical characteristics of tan δ, insulation resistance (IR), and pulse voltage were measured, and the results are shown in Table 1.

[Table] In Table 1, sample numbers 2 to 5 and 7 to 9 are related to the present invention, and sample numbers 1, 6, and 10 are characteristic diagrams shown for reference and are outside the scope of the present invention. Example 2 BaCO ₃ , TiO ₂ , ZrO ₂ , SnO ₂ ,
MnO and Nb ₂ O ₅ were weighed to give the composition shown in Table 2. A/B shown in Table 2 is Ba _A (Ti _1-xy Zrx Sny)
This shows the composition ratio when _B O ₃ is used. These weighed starting materials were wet mixed together with water and agate cobbles in a polyethylene pot for about 16 hours.
A prepared raw material was obtained by filtering and drying. The same method as in Example 1 was used below.

【table】

[Table] In Table 2, sample numbers 2-5, 7-9, 11-
12, 14-16, 18-23 are products of the present invention, sample number 1,
Items 6, 10, 13, and 17 are shown for reference and are outside the scope of the present invention. Note that the electrical properties shown in Tables 1 and 2 are capacitance (permittivity) and tan δ measured at 1 KHz and 1 Vrms, and insulation resistance is the value after applying 100 VDC for 30 seconds. When the nonlinear ceramic capacitor according to the present invention is connected in series with the nonlinear ceramic capacitor 3 and the dielectric element 1 as shown in FIG. 1, a pulse waveform as shown in FIG. 2 (b) is observed. 2 is load resistance, 4
is a commercial frequency power supply, and Figure 2A is a commercial frequency voltage waveform. That is, the nonlinear ceramic capacitor according to the present invention has good square hysteresis as shown in FIG. 3, and the voltage division of Do, which is the amount of spontaneous polarization, changes suddenly near voltages Eo and -Eo, and charging current flows. When the voltage exceeds Eo and reaches Es, the amount of charge is saturated and charging current no longer flows. Due to this switching action of the charging current, a pulse voltage as shown in FIG. 2B corresponding to the back electromotive force is obtained from the inductive element. That is, to explain an application example in a fluorescent lamp lighting device, FIG. 4 shows an embodiment of a circuit of a pulse generator for non-contact starting of a fluorescent lamp using the nonlinear ceramic capacitor of the present invention. an inductive element, 3 a nonlinear ceramic capacitor according to the present invention, 4 a commercial frequency power supply, 5 a fluorescent lamp, 5
1 and 52 are the filaments of a fluorescent lamp, and 6 is a switching circuit. When the switching circuit 6 adjusts the voltage applied to the nonlinear ceramic capacitor as shown in Figure 5 (a), an extremely high pulse is generated as shown in Figure 5 (b). It can induce voltage. In the AC waveform, if the switching circuit 6 is turned OFF at point a of Es in Figure 5A and turned ON at point b before the voltage reaches -Es, the inductance shown in Figure 4 will be The induced voltage (Ldi/dt) due to the element 1 and the nonlinear ceramic capacitor 3 can generate an extremely high pulse voltage as shown in FIG. 5B. Connect the switching circuit at point C in Figure 5A.
When turned on, pulses are generated in the negative direction, so b
It is necessary to turn it on at the point. When the waveform shown in FIG. 5B is applied to the circuit of the fluorescent lamp shown in FIG. filament 51,
52 is heated, a discharge is induced by the pulse at point a in FIG. 5B, and the light is turned on. The pulse voltages of the nonlinear ceramic capacitors having a ceramic composition according to the present invention shown in Examples 1 and 2 were measured using the circuit shown in FIG. From the results shown in Table 1, it was found that a high pulse voltage can be obtained in Ba(Ti _1-xy ZrxSny)O ₃ by substituting a part of Ti in BaTiO ₃ with Zr and Sn. In particular, a major feature of the present invention is that it can obtain a high pulse voltage over a wide temperature range.
Comparing a product containing 2 mol% of zirconium and 7 mol% of zirconium with a product containing no zirconium, as shown in Figure 6, the conventional product
For the product containing only Sn and no zirconium, the pulse voltage decreases rapidly at about 30℃, but for the product containing 7 mol% of zirconium of the present invention, the pulse voltage can be high up to about 70℃. can get. The temperature dependence of this pulse voltage seems to depend on the crystal structure of the barium titanate solid solution, and it seems that a high pulse voltage can be obtained in an orthorhombic crystal structure, but even in an orthorhombic crystal structure, This does not mean that a high pulse voltage can be obtained;
The reason for this is still not clear. It should be noted that if the zirconium content exceeds 14 mol %, the pulse voltage will decrease, which is not preferable. Although MnO was used as an additive in the examples,
Similar results can be expected with other Mn compounds.
When the amount of MnO and Nb ₂ O ₅ added exceeds 0.5% by weight, not only the insulation resistance decreases but also the pulse voltage becomes low. The pulse voltage is approximately 400V under the best fluorescent lamp conditions.
If so, it is possible to turn on the light, and this is made a limiting condition for the scope of the claims. The effect of MnO and Nb ₂ O ₅ is obvious even when added in a trace amount of 0.01% by weight. In addition, in barium titanate solid solution (ABO ₃ ), the highest pulse voltage is desirable when the A/B ratio is around 1.0, but in the case of B-rich, the firing temperature can be lowered as in the case of ordinary ceramic capacitors. On the other hand, in the case of A-rich, the crystal grains of the porcelain body become slightly smaller and the strength of the porcelain body can be increased. In the present invention, the A/B ratio is not limited to 1.0 as described above. The feature of the present invention is not only the magnitude of the pulse voltage but also the excellent temperature dependence of the pulse voltage. That is, conventional nonlinear ceramic capacitors cannot obtain a high pulse voltage in a high temperature range, and have an upper temperature limit of 30° C., making them difficult to put into practical use due to the narrow range of operating temperatures. The present invention expands this upper limit temperature to 60 to 80°C, and can significantly expand the range of uses. It has not yet been theoretically clarified why the composition of the present invention has a high upper limit temperature range. In the present invention, a polycrystalline solid solution of Ba(TiZrSn) _O3 has been described, but in this composition having a perovskite crystal structure, a part of Ba contains Pb, Sr,
It is clear that similar effects can be expected by replacing solid solution components such as Ca. The reason for choosing the Ba(TiZrSn) _O3 composition is as follows. In other words, to obtain a high pulse voltage at high temperatures, it is sufficient to add Zr, but to obtain a high pulse voltage at temperatures of 60 to 80°C, it is necessary to add 8 to 10 mol% of Zr. If too much is added,
The sintering temperature becomes high, which is undesirable, and the addition of Sn, preferably 1 to 6 mol %, lowers the sintering temperature. Furthermore, compared to the case of adding Zr alone, the addition of Sn and Zr2 components can increase ε, which has the effect of making it possible to reduce the size. The nonlinear ceramic capacitor having a ceramic composition according to the present invention can be used not only for lighting fluorescent lamps, but also for starting lighting devices for city gas, propane gas, and discharge lamps such as mercury lamps and sodium lamps that require high-voltage pulses. It has a wide range of potential applications in circuits and other pulse generators, and could make a significant contribution to the electronics industry.

[Brief explanation of the drawing]

Figure 1 shows a pulse waveform measurement circuit for the nonlinear ceramic capacitor of the present invention, Figure 2 shows the waveform diagram in Figure 1, A is a commercial frequency voltage waveform diagram, and B is the voltage applied across the nonlinear ceramic capacitor of the present invention. 3 is a hysteresis characteristic diagram of the nonlinear ceramic capacitor of the present invention. FIG. 4 is a circuit diagram of an embodiment of a pulse generator for non-contact starting of a fluorescent lamp using the nonlinear ceramic capacitor of the present invention. Figure 5 is a diagram of the pulse voltage waveform applied by the circuit of Figure 4, A is the voltage waveform applied to the nonlinear ceramic capacitor of the present invention, B is the voltage waveform induced by the inductive element, and Figure 6 is the waveform of the voltage applied to the nonlinear ceramic capacitor of the present invention. FIG. 3 is a temperature characteristic diagram of pulse voltage of the nonlinear ceramic capacitor of the invention and the conventional product A.

Claims (1)

[Claims] 1. Consists of a polycrystalline body whose composition is Ba(Ti _1-XY
A nonlinear ceramic capacitor characterized by consisting of ZrxSny) _O3 . However, 0.01≦x≦0.14 0.01<y≦0.15 2 At least one of the Mn and Nb compounds in the polycrystalline body is converted into an oxide (MnO, Nb ₂ O ₅ ).
Claim 1 comprising 0.5% by weight or less
Nonlinear ceramic capacitors as described in Section. 3. The nonlinear ceramic capacitor according to claim 1 or 2, which is used as a starting element for a pulse generator.