KR100389377B1 - Composition and fabrication method of electrostrictive ceramic for a high voltage devision and current supplement device - Google Patents

Abstract

The present invention relates to an electrodistortion ceramic composition for high voltage partial pressure and current supply, and a method for preparing the same, wherein the composition is 0.55Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.3BaTiO ₃ -0.15PbTiO ₃ and 0.8c A specimen is prepared by mixing and sintering HTc ceramic of Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.1BT-0.1PT. In the manufacturing method, the sample is weighed with an electronic balance, and the first sample is mixed and pulverized for a predetermined time by mixing and grinding the weighed sample with acetone in a mixed medium. The calcined and calcined samples were mixed and pulverized with acetone in a ball mill for a predetermined time in a ball mill for a predetermined time, and after mixing and pulverizing the second, a predetermined amount of PVA solution was added to a dried sample and a circular molder having a predetermined size was used. After molding at a constant pressure, the molded sample is secondarily baked at a predetermined temperature for a predetermined time, and then, the prepared specimen is polished to a predetermined thickness and manufactured by polishing and electrode coating to apply an electrode.

Description

Composition and fabrication method of electrostrictive ceramic for a high voltage devision and current supplement device

The present invention relates to a whole-distortion ceramic composition for high voltage partial pressure and current supply and a method of manufacturing the same.

In general, the power supply system of the process switchgear for distribution automation has a structure in which a condenser and a winding transformer are connected in series, and the line voltage is divided by a high voltage capacitor to divide the high voltage to a low voltage by a winding transformer, and then the secondary side of the winding transformer. It is a system to secure the power from.

However, in the related art, since the dielectric constant of the voltage dividing element is small and the dielectric constant changes significantly with temperature, a larger input voltage is required than the winding transformer to supply an appropriate current, so that the volume of the winding transformer becomes large, and the operating current according to temperature. Supply had the disadvantage of being inconsistent.

Therefore, in order to secure a stable current source with a small size, the dielectric constant of the voltage dividing element having the high voltage is divided, and a voltage dividing element having a small change in the dielectric constant with temperature is required.

In addition to the BaTiO ₃ series ceramics as the composition for the high voltage partial pressure, there are Pb (Zn _1/3 Nb _2/3 ) O ₃ based ceramics capable of securing sufficient capacity as a dielectric distortion ceramics for high voltage partial pressure.

The Pb (Zn _1/3 Nb _2/3 ) O ₃ ceramic is a ferroelectric having a partially disordered perovskite structure, which exhibits a diffusion phase transition near 140 ° C., and crystal symmetry is trigonal at room temperature and Curie temperature. It is cubic system beyond 140 degrees Celsius.

In Pb (Zn _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PZN-PT) system, phase boundary (MPB) is trigonal (PZN) and tetragonal (PT) near 9 mol% of tetragonal system (PT) Exists between).

It has a large dielectric constant, but unfortunately, it is very difficult to synthesize the trigonal-orthogonal (PZN-PT) ceramic and perovskite structure trigonal (PZN) near the phase boundary (MPB) by the usual solid-phase reaction method. it's difficult.

The material obtained by the solid phase reaction at 1100 ° C. is a mixture containing a stable cubic pyrochlore phase, the formation of which affects both dielectric and piezoelectric properties.

In the trigonal-square system (PZN-PT) system, the perovskite phase is stable only when the tetragonal (PT) content exceeds 25 mol%.

However, as shown in FIG. 1, when BaTiO ₃ is added as a third component to a trigonal-quadratic system (PZT-PT) system, trigonal (PZN) ceramic having a 100% perovskite structure can be manufactured. .

PZN-BT-PT system has excellent characteristics such as high dielectric constant, moderate dielectric constant with temperature, excellent direct current (DC) stability, low sintering temperature, etc. The method has the disadvantage that the temperature stability of the dielectric constant is very poor, because there is advantageously only one phase transition peak on the ε-T curve.

In order to solve the above disadvantages, an object of the present invention is to provide a method for producing a whole-distortion ceramic composition made of ternary ceramics having a relatively large dielectric constant applicable to a high voltage voltage dividing element and a current source and a small change in dielectric constant with temperature. It is done.

The present invention for achieving the above object is 0.55Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.3BaTiO ₃ -0.15PbTiO ₃ LTc ceramic and 0.8Pb (Zn _1/3 Nb _2/3 ) O ₃ It is characterized in that the specimen is prepared by mixing and sintering the ceramic of -0.1BT-0.1PT.

The manufacturing method according to the present invention comprises a first step of weighing a sample with an electronic balance, a second step of first mixing the ground weight sample with acetone in a ball mill with a mixed medium, pulverizing and drying, and drying A third step of firstly calcining the sample for a predetermined time, a fourth step of mixing the calcined sample with acetone in a ball mill for a predetermined time in a ball mill, and then pulverizing and drying the second sample, followed by drying after the second mixing A fifth step of adding a predetermined amount of PVA solution to the prepared sample and molding at a constant pressure using a circular molder of a predetermined size, a sixth step of secondary baking the molded sample at a predetermined temperature for a predetermined time, and And a seventh step of applying the electrode by grinding the calcined specimen to a predetermined thickness.

1 is a top view cross-sectional structure diagram of a conventional PZN-BT-PT ceramic.

2 is a temperature dependent characteristic diagram of a dielectric constant for the (1-X) LTc-XHTc PZN-BT-PT ceramic of the present invention.

Figure 3 is a flow chart of the mixed sinter manufacturing process to which the present invention is applied.

Figure 4 is a dielectric constant change characteristic according to the specimen temperature of the present invention.

5a to 5c is a hysteresis curve characteristic diagram according to the specimen of the present invention.

6a to 6e is a hysteresis curve characteristics according to the temperature of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a temperature dependent characteristic diagram of the dielectric constant for the (1-X) LTc-XHTc PZN-BT-PT ceramic of the present invention.

That is, Figure 2 shows the temperature dependence of the dielectric constant for (1-X) LTc-XHTc PZN-BT-PT ceramic.

The temperature characteristics of the dielectric constant of the relaxed ferroelectric can be efficiently improved by using the mixed sintering method.Halliyal et al., Said, the position of the transition peak of the PZN solid solution in the PZN-BT-PT system is -140 depending on the amount of other BT / PT. It is possible to vary the temperature range from ° C to 490 ° C.

It is possible to produce mixed-sintering ceramics (hereinafter referred to as MSCs) in PZN-BT-PT systems with different compositions, ie using different solid solutions with different transition temperatures.

In the present invention, the MSC is prepared in the PZN-BT-PT system, and the dielectric properties and temperature stability of the dielectric constant thereof are presented. The Curie temperatures (Tc) of pure PZN and BaTiO ₃ are 140 ° C. and 120 ° C., respectively.

However, the solid solution Tc between PZN and BT decreases from 140 ° C to -140 ° C as the amount of BT increases in the PZN-BT system.

In addition, the Tc is changed in a wide temperature range by changing the BT amount and the PT amount in the PZN-BT-PT system.

Therefore, a composite ceramic having a temperature stability of dielectric constant in the temperature range of -25 ° C to 50 ° C can be designed using two compositions having different Tc of about -40 ° C and 100 ° C.

In the present invention, the Tc is selected from the composition of the LTc, HTc two components of -35 ℃ and 100 ℃, respectively, if the two phases can be mutually present during sintering, the dielectric constant of the composite (logarithmic mixing) rule) can be calculated as in Equation 1 below.

Ε ₁ and ε ₂ are the dielectric constants of the constituents, X ₁ and X ₂ are their volume ratios, and (1-X) LTc-XHTc shows the result calculated according to Equation 1 as the composition ratio X changes. 2 is shown.

Figure 3 is a flow chart of a mixed sintering manufacturing process to which the present invention is applied, showing a flow of a method for producing a high voltage partial pressure and a total distortion ceramic composition for a current source.

As shown in FIG. 3, the method of manufacturing the whole-distortion ceramics composition of the present invention provides the amount of PbO, ZnO, Nb ₂ O, BaCO ₃ , TiO ₃ constituting the LTc ceramic and the HTc ceramic as a sample for preparing the composition. A step of weighing (S1), a first mixing and grinding step (S2) of mixing and grinding the sample weighed in the weighing step with acetone in a mixed medium for 24 hours in a ball mill, the sample completely dried in the first mixing and grinding step The first firing step (S3) for the first firing at 900 ℃ for 6 hours, the second firing mixing and pulverizing the sample calcined first in the first firing step in a ball mill with a mixed medium for 2 hours in a ball mill And pulverizing (S4), adding 5 wt% of 5% PVA solution to the sample dried in the second mixing and pulverizing step to form a pressure of ¹ ton / cm ² using a circular molder having a diameter of 21 mm ( S5), the sample molded in the forming step Secondary firing at 1075 ° C. for 1 hour (S6), polishing the specimen fired in the secondary firing step to a thickness of 1 mm to apply an electrode (S7), and applying the electrode at the electrode applying step. The measuring step (S8) to measure the dielectric properties of the specimen is carried out.

The specimen was prepared by the mixed sintering method of the LTc ceramic of Formula 1 and the HTc ceramic of Formula 2 at a mixing ratio of x = 0.4, 0.5, and 0.6.

LTc Ceramic: 0.55 Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.3 BaTiO ₃ -0.15 PbTiO ₃

HTc Ceramic: 0.8Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.1BT-0.1PT

(1-X) [0.55Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.3BaTiO ₃ -0.15PbTiO ₃ ] -X [0.8Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.1BT- 0.1PT] (X = 0.4, 0.5, 0.6)

Each of the ceramics of LTc and HTc was mixed and pulverized with acetone in a ball mill for the first time in a ball mill (S1), which was aliquoted in the composition ratio of Chemical Formula 1 and Chemical Formula 2 (S2), and then completely dried at 900 ° C. Prepared by primary firing (calcination) for a time (S3).

After the manufacture of each ceramic, the first calcined LTc ceramics and HTc ceramics were mixed at their respective composition ratios (X), mixed and ground in a ball mill for 24 hours (S4), and after complete drying, polyvinyl alcohol (PVA) ) (5 wt% aqueous solution is added 5wt%) The solution is mixed, and then molded at a pressure of 1ton / cm ^{2 with} a circular molder having a diameter of 21mm (S5).

The sample thus formed is fired for 1075 ° C. (S6), and the fired specimen is polished to a thickness of 1 mm to apply an electrode (S7).

At this time, the density is obtained by measuring the specimen in water and in air, and the dielectric constant is obtained by measuring the capacitance when the frequency is 1KHz using an LCR meter (ANDO).

After the electrode coating (S7), the constant electric field (Ec) and the split electrode (Pr) are obtained using a sawtower circuit (S8).

As described above, FIG. 3 shows a method of manufacturing a composite ceramic using two compositions having different Curie temperatures.

Table 1 shows the types and densities of the specimens for the experimental composition according to the present invention.

Specimen Classification and Density Composition, density Mixed composition Firing Density (g / cm ³ ) S1 0.4 (HTc) -0.6 (LTc) 7.51 S2 0.5 (HTc) -0.5 (LTc) 7.59 S3 0.6 (HTc) -0.4 (LTc) 7.64

The basic composition of the composite ceramic manufacturing method was 0.55PZN-0.3BT-1.5PT as LTc ceramic, 0.8PZN-0.1BT-0.1PT as HTc, and the specimens were mixed as shown in Table 1 in the order shown in FIG. The density of S1 was 7.51, S2 was 7.59, and S3 was 7.64, respectively.

This value is much higher than the fabricated BaTiO ₃ -based ceramics, and it is possible to improve the breakdown voltage and breakdown strength even under high voltage in the application of the partial pressure predistortion ceramics used to secure an operating current source.

Figure 4 is a characteristic of the dielectric constant change according to the temperature of the specimen of the present invention, showing the dielectric constant changes with temperature for the three mixtures.

In view of the characteristic, as a result of calculating Δε / ε%, S1 was 14%, S2 was 10%, and S3 was 10%, respectively.

It can be seen that the capacitor capacitance for the high voltage voltage divider used up to now is considerably smaller than the variation of up to 40%. In addition, the hysteresis loop of the electrostrictive ceramics having excellent temperature stability should have a small area change of the curve with temperature and a small curve area with a small curve area.

In the present invention, the saturation polarization field of the specimen having a diameter of 18 mm and a thickness of 1 mm was calculated from the hysteresis characteristics, and the fineness was found to be as high as 28 KV / cm at room temperature. Therefore, it can be interpreted to be able to withstand up to 28KV when the specimen is produced with a thickness of 1cm, it is possible to apply this composition as a device for partial pressure.

In addition, since the area of the hysteresis is very small to show a fine curve, the dielectric loss is small and heat generation can be reduced under high voltage.

In addition, 5a to 5c is a hysteresis curve characteristic diagram according to the specimen of the present invention, showing the hysteresis characteristics at room temperature for the three mixture composition.

Figure 6a to 6e is a hysteresis characteristic diagram according to the temperature of the present invention, showing the hysteresis characteristics according to the temperature change in the S2 specimen, the temperature characteristic is good enough to hardly observe the area change of this curve with the temperature change It can be seen.

In the experiment according to the present invention for developing PZT-BT-PT ceramics as a device for high voltage partial pressure and current source, the characteristics thereof were analyzed and the following results were obtained.

(1) The PZT-BT-PT composite for ceramics for partial pressure showed a very stable temperature characteristic of 10% at the composition ratio of -25 ℃ to 50 ℃ by controlling the composition ratio.

(2) The saturation polarization field of the specimen was high at 28KV / cm in all three compositions, indicating that it is suitable for high voltage use.

(3) The hysteresis of the specimen shows a fine curve, so that the dielectric loss is small. Therefore, the hysteresis of the specimen is excellent in the long-term use of the high voltage drop because of the low heating effect when used under high voltage.

(4) In the case of S2 specimen with excellent temperature stability of dielectric constant, dielectric constant at room temperature was 6800, which showed very good characteristics as current source voltage divider.

According to the present invention, the method for manufacturing a high-voltage partial-voltage and current-distortion ceramic composition according to the present invention is a manufacturing technique of a voltage-dividing element capable of reducing the size of a conventional winding-type transformer and a total-distortion ceramic composition ratio of a capacitor capable of maintaining a stable voltage-division ratio according to temperature. The establishment of technology and its application to a gas-opening built-in operating current supply device, which is expected to be in rapid demand, have the effect of realizing a capacitor for voltage and current supply that can be used as a high voltage measuring device.

Claims (9)

0.45 to 0.6 mol LTc ceramic having a composition of 0.55 Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.3 BaTiO ₃ -0.15 PbTiO ₃ , and 0.8 Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.1 A high voltage partial pressure and current supply pretreatment film composition for supplying a high voltage partial pressure and current having a specimen shape in which 0.4 to 0.6 mol of HTc ceramic having a composition of BT-0.1PT is mixed and sintered. The method of claim 1, The HTc and LTc ceramic is a ceramic composition for high voltage partial pressure and current supply, characterized in that when the composition ratio is 0.5 mol, the temperature characteristic of the dielectric constant is 10%, the dielectric constant is 6800 at room temperature. A first step of weighing a sample obtained by mixing and sintering 0.4-0.6 mol LTc ceramic and 0.4-0.6 mol HTc ceramic with an electronic balance, A second step of firstly mixing the weighed sample with acetone in a ball mill in a ball mill for 24 hours, pulverizing and drying the powder; A third step of first baking the dried sample at 900 ° C. for 6 hours; A fourth step of mixing the calcined sample with acetone in a ball mill for 2 hours in a ball mill for 2 hours, pulverizing and drying the powder; A fifth step of adding 5 wt% polyvinyl alcohol (PVA) solution to the dried sample after the second mixing and molding at a pressure of ¹ ton / cm ² using a circular molder having a diameter of 21 mm, A sixth step of second firing the sample molded by the circular molder at 1075 ° C. for one hour; And a seventh step of applying the electrode by polishing the secondary fired specimen to a thickness of 1 mm. The method of claim 3, wherein The first step is a method for producing a high-voltage pre-distortion ceramics composition for supplying high voltage and current, characterized in that the basis weight of the LTc and HTc ceramic composition. The method of claim 4, wherein The composition of the LTc ceramic is 0.55Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.3BaTiO ₃ -0.15PbTiO ₃ , and the composition of HTc ceramic is 0.8Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.1BT-0.1PT method for producing a high voltage partial pressure and current supplying electro-ceramic composition for the composition. delete The method of claim 4, wherein A method of manufacturing a high voltage partial pressure and current supplying electrostrictive ceramic composition, characterized in that for controlling the temperature characteristic and dielectric constant of the dielectric constant by adjusting the composition ratio (x) of the LTc and HTc ceramics. delete The method of claim 7, wherein The temperature characteristic of the dielectric constant of the ceramic composition is determined by the conditions for sintering after primary calcining, mixing and pulverizing PZN-BT-PT-based ceramics having different phase transition temperatures, respectively. Method of Preparation of the Composition.