JPH0132647B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a nonlinear ceramic capacitor made of a ferroelectric ceramic composition containing barium titanate as a main component, and is characterized in that it generates high voltage pulses by coupling with an inductive element. 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. In addition, it has the disadvantage that the pulse voltage varies widely, and it also has the fatal disadvantage that the pulse voltage drops rapidly 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. In other words, it was discovered that by incorporating zirconium into a barium titanate solid solution having a perovskite crystal structure and adding a trace amount of an alkali metal compound, a high pulse voltage can be obtained with good reproducibility over a wide temperature range. Hereinafter, the present invention will be explained in detail based on examples. As starting materials, BaCO ₃ , TiO ₂ , ZrO ₂ , and alkali metal carbonate were weighed at the mixing ratio shown in Table 1, wet-mixed with acetone and agate stones in a polyethylene pot for about 16 hours, filtered, and dried. I got the raw material. This was calcined at 1120°C for 2 hours, ball-milled in acetone for 16 hours, filtered, and dried. Approximately 3.0% by weight of an organic binder was added to the raw material to make it into granules, which were then pulverized to a diameter of 1 ton/cm ² under a pressure of 1 ton/cm 2. 16.0mm
Form into a disk shape with a diameter of 0.65 mm and a thickness of 0.65 mm. then 1400
A silver electrode of 12.0 mmφ is coated on the porcelain obtained by firing at 800°C for 2 hours, and an element for a nonlinear ceramic capacitor is obtained by baking at 800°C for 30 minutes. The electrical characteristics of the capacitor element thus obtained were measured, including dielectric constant, tan δ, insulation resistance (IR), and pulse voltage, and the results are shown in Table 1.

【table】

[Table] In Table 1, sample numbers 11-13, 15, 17-
19, 21-23, 25-27, 29-38 are within the scope of the present invention, sample numbers 1-10, 14, 16, 20, 24, 28,
Nos. 39 and 40 were outside the scope of the present invention. In addition, when measuring the electrical characteristics shown in Table 1,
Capacitance (permittivity) and tan δ are measured at a frequency of 1 KHz and 1 Vrms, and insulation resistance (IR) is the value after applying 100 VDC for 30 seconds. Further, the pulse voltage was measured using the circuit shown in FIG. In the examples, an alkali metal carbonate was used as the starting material, but similar results can be expected with other alkali metal compounds, and the amount of alkali metal oxide added was 0.5% by weight. If it exceeds this, the pulse voltage will be low, and under the best conditions for a fluorescent lamp lighting device, lighting can be achieved with a pulse voltage of about 400 V.
This is a limiting condition for the scope of the claims. In addition, even in compositions without adding alkali metal compounds, 0.01<
A system in which Zr is dissolved as a solid solution in the range of x<0.14 can obtain good properties, but by adding an alkali metal compound, porcelain with even more stable and good properties can be obtained. In barium titanate solid solution (ABO ₃ ), the highest pulse voltage is desirable when the A/B ratio is around 1.0, but if there is an excess of B, the firing temperature can be lowered, just as in a normal ceramic capacitor; In this case, the crystal grain size of the porcelain body becomes slightly smaller and the mechanical 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 that by adding an alkali metal compound to a composition containing 1 to 14 mol% of zirconium as a solid solution, the pulse voltage can be increased without impairing its excellent temperature characteristics. In the present invention, a polycrystalline solid solution of Ba(Ti ₁ −x, Zrx)O ₃ has been described, but in this composition having a perovskite crystal structure, a part of Ba contains Pb,
It is clear that similar effects can be expected by substituting Sr, Ca, etc., or a solid solution component such as Sn for a part of Zr. The nonlinear ceramic capacitor of the present invention manufactured in this way has an inductive element 1 as shown in FIG.
When connected in series, a pulse waveform as shown in FIG. 2B is observed. 2 is a load resistor, 4 is a commercial frequency power source, and FIG. 2A is a commercial frequency voltage waveform diagram. In other words, the nonlinear ceramic capacitor according to the present invention has good square hysteresis as shown in Fig. 3, and near the voltages _E0 and _-E0 , the charge of _D0 , which is the amount of spontaneous polarization, changes suddenly and a charging current flows. However, when the voltage exceeds E ₀ 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 is obtained from the inductive element as shown in FIG. 2B, which corresponds to the back electromotive force. FIG. 4 shows an embodiment of a pulse generator circuit for non-contact starting of a fluorescent lamp using the nonlinear ceramic capacitor of the present invention, in which 1 is an inductive element, 3 is a nonlinear ceramic capacitor according to the present invention, and 4 is a commercially available pulse generator. frequency power supply,
5 is a fluorescent lamp, 5 ₁ , 5 ₂ is a fluorescent lamp filament, 6
is a switching circuit which, when the switching circuit 6 adjusts the voltage applied to the nonlinear ceramic capacitor as shown in FIG. 5A, can induce an extremely high pulse voltage as shown in FIG. 5B. In the AC waveform, the switching circuit 6 is turned OFF at point a of Es in Figure 5A, and the switching circuit 6 is turned ON at point b before the voltage reaches -Es, resulting in the induction shown in Figure 4. The induced voltage (Ldi/dt) due to the magnetic element 1 and the nonlinear ceramic capacitor can generate an extremely high pulse voltage as shown in FIG. 5B. In Figure 5 A, connect the switching circuit at point C.
When turned on, pulses are generated in the negative direction, so
It is necessary to turn it on at point b. Furthermore, when the waveform shown in FIG. _5B is applied to the circuit of the fluorescent lamp shown in _FIG . Then,
The filaments 5 ₁ and 5 ₂ of the fluorescent lamp 5 are heated, and a discharge is induced by the pulse at point a in FIG. 5B, causing the lamp to turn on. The temperature characteristics of pulse voltage and dielectric constant are shown in Figures 6 and 7. Conventional nonlinear ceramic capacitors cannot obtain high pulse voltage in the high temperature range, and the upper limit temperature is 30°C, which is the operating temperature. The range was too narrow to be practical. The present invention expands this upper limit temperature to 60 to 80°C, and can significantly expand the range of uses. The nonlinear ceramic capacitor having a ceramic composition according to the present invention is useful not only for lighting conventionally used fluorescent lamps, but also for lighting devices that require high-pressure pulses, such as city gas, propane gas igniters, mercury lamps, and sodium lamps. The present invention is useful for a wide range of applications, such as lighting starting circuits for discharge lamps such as the above, and other pulse generators.

[Brief explanation of drawings]

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. A waveform diagram, FIG. 3 is a hysteresis characteristic diagram of the nonlinear ceramic capacitor of the present invention, and 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. 5 is a pulse voltage waveform diagram applied by the circuit of FIG. 4, A is a voltage waveform applied to the nonlinear ceramic capacitor of the present invention, B is a voltage waveform induced by an inductive element, and FIG. FIG. 7 is a temperature characteristic diagram of the pulse voltage of a nonlinear ceramic capacitor induced by an inductive element, and FIG. 7 is a temperature characteristic diagram of the dielectric constant of the nonlinear ceramic capacitor.

Claims (1)

[Claims] 1. Consists of a polycrystalline body whose composition is Ba(Ti ₁ -x,
Zrx) O ₃ with at least one alkali metal compound oxide (Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O,
A nonlinear ceramic capacitor characterized by containing 0.5% by weight or less of Cs ₂ O). However, x=0.01 to 0.14 2 The nonlinear ceramic capacitor according to claim 1, which is used as a starting element of a pulse generator.