JP2008297133A - Dielectric porcelain and capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric porcelain exhibiting a high dielectric constant and stable temperature properties in a specific dielectric constant and having reduced spontaneous polarization and to provide a capacitor using it. <P>SOLUTION: The dielectric porcelain comprises crystal grains containing barium titanate as a main ingredient, calcium, magnesium, a rare earth element and manganese and grain boundary phases and contains calcium of 0.1 mole or less in terms of CaO, magnesium of 0.01-0.064 mole in terms of MgO, a rare earth element of 0.0015-0.03 mole in terms of RE<SB>2</SB>O<SB>3</SB>and manganese of 0.0002-0.03 mole in terms of MnO to titanium 1 mole constituting barium titanate. The crystal structure of the dielectric ceramic identified by X-ray diffraction is mainly cubic. The average crystal grain diameter of the crystal grains is 80-200 nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic made of crystal particles mainly composed of barium titanate and a capacitor using the dielectric ceramic.

  At present, the spread of digital electronic devices such as mobile computers and mobile phones is remarkable, and in the near future digital terrestrial broadcasting is going to be deployed nationwide. There are a liquid crystal display, a plasma display, and the like as digital electronic devices that carry digital terrestrial broadcasting, and many LSIs are used for these digital electronic devices.

Therefore, many bypass capacitors are mounted on the power supply circuits that make up these digital electronic devices such as liquid crystal displays and plasma displays, but the capacitors used here require high capacitance. In some cases, a high dielectric constant monolithic ceramic capacitor (for example, see Patent Document 1) is adopted. On the other hand, when temperature characteristics are important even with a low capacitance, a temperature compensation type monolithic ceramic capacitor with a small capacitance change rate (for example, Patent Document 2) is adopted.
JP 2000-58377 A JP 2001-294482 A

  However, since the multilayer ceramic capacitor having a high dielectric constant disclosed in Patent Document 1 is composed of crystal grains of dielectric ceramic having ferroelectricity, the temperature change rate of relative permittivity is large and exhibits dielectric polarization. There was a problem of large hysteresis.

  In addition, a capacitor formed by using a ferroelectric dielectric ceramic disclosed in Patent Document 1 tends to generate a “sounding” phenomenon caused by an electrically induced strain on a power supply circuit. It was an obstacle when using it.

  On the other hand, the temperature-compensated monolithic ceramic capacitor has the advantage that there is no hysteresis showing dielectric polarization because the dielectric ceramic that constitutes it is paraelectric, and no electrical distortion specific to ferroelectricity occurs. Since the dielectric ceramic has a low relative dielectric constant, there is a problem in that the storage capacity is low and the performance as a bypass capacitor is not satisfied.

  Accordingly, an object of the present invention is to provide a dielectric ceramic that exhibits a temperature characteristic of a high dielectric constant and a stable relative dielectric constant and has a small spontaneous polarization, and a capacitor using the dielectric ceramic.

The dielectric ceramic according to the present invention is a dielectric ceramic composed mainly of barium titanate and comprising crystal grains containing calcium, magnesium, rare earth elements, and manganese and a grain boundary phase, and constitutes the barium titanate. With respect to 1 mol of titanium, calcium is 0.1 mol or less in terms of CaO, magnesium is 0.01 to 0.064 mol in terms of MgO, and rare earth elements are 0.0015 to 0.03 mol in terms of RE ₂ O ₃ , And manganese in a range of 0.0002 to 0.03 mol in terms of MnO, the crystal structure identified by X-ray diffraction of the dielectric ceramic is mainly composed of a cubic system, and The crystal grain has an average crystal grain size of 80 to 200 nm.

  In the dielectric ceramic, the calcium content is 0.025 to 0.075 mol in terms of CaO, the magnesium content is 0.01 to 0.04 mol in terms of MgO, and the crystal particles It is desirable that the average crystal grain size is 130 to 200 nm.

  The capacitor according to the present invention is characterized in that a dielectric layer made of the above dielectric ceramic and a conductor layer are laminated.

  According to the dielectric ceramic of the present invention, the dielectric ceramic mainly composed of barium titanate contains calcium, magnesium, rare earth element and manganese in the above-mentioned ratio in terms of oxides, and X of the dielectric ceramic. The crystal structure identified by the line diffraction is mainly composed of a cubic system, and the average grain size of the crystal grains is set to 80 to 200 nm, so that the dielectric constant is higher than that of a conventional dielectric ceramic having ferroelectricity. Dielectric porcelain having a low rate of change in temperature, a high dielectric constant compared to conventional dielectric ceramics having paraelectric properties, stable temperature characteristics of relative dielectric constant, and low spontaneous polarization Can be obtained.

  In the dielectric ceramic of the present invention, the calcium content is 0.025 to 0.075 mol in terms of CaO, the magnesium content is 0.01 to 0.04 mol in terms of MgO, and When the average crystal grain size of the crystal particles is 130 to 200 nm, a dielectric ceramic having a higher relative dielectric constant, more stable temperature characteristics of the relative dielectric constant, and smaller spontaneous polarization can be obtained.

  Further, according to the capacitor of the present invention, the dielectric layer exhibits temperature characteristics of a high dielectric constant and a stable relative dielectric constant, and by applying the above-described dielectric ceramic having a small spontaneous polarization, it is possible to make the dielectric layer more than conventional capacitors. Capacitors with high capacitance and stable capacitance-temperature characteristics can be formed. When this capacitor is used for a power supply circuit, it is possible to suppress the occurrence of a “sounding” phenomenon caused by electrically induced distortion.

The dielectric porcelain of the present invention is composed essentially of crystal grains containing barium titanate as a main component and containing calcium, magnesium, rare earth elements and manganese, and a grain boundary phase. Calcium is 0.1 mol or less in terms of CaO, magnesium is 0.01 to 0.064 mol in terms of MgO, and rare earth elements are 0.0015 to 0 in terms of RE ₂ O ₃ with respect to 1 mol of titanium constituting barium. 0.03 mol and manganese are contained at a ratio of 0.0002 to 0.03 mol in terms of MnO.

  In the dielectric ceramic according to the present invention, the crystal structure identified by X-ray diffraction of the dielectric ceramic is mainly composed of a cubic system, and the average crystal grain size of crystal grains constituting the dielectric ceramic is 80. It is important to be ~ 200 nm.

  When the above composition and particle size are used, and the crystal structure is mainly composed of a cubic system, the relative dielectric constant at room temperature is 410 or more, and the change rate of the relative dielectric constant between −55 ° C. and 125 ° C. is ± 10%. There is an advantage that a dielectric ceramic having a small hysteresis in dielectric polarization can be formed.

  In such a dielectric ceramic of the present invention, the crystal particles are obtained by solidly dissolving barium titanate with calcium, magnesium, rare earth elements and manganese, and these components are mainly composed of barium titanate. By setting the average crystal grain size of the crystal particles to 80 to 200 nm, the crystal structure of the dielectric porcelain constituted by the crystal particles can be mainly composed of a cubic system. Ferroelectricity due to the crystal structure is reduced, paraelectricity can be increased, and spontaneous polarization can be reduced by increasing paraelectricity.

  Further, by making the crystal structure of the crystal grains mainly a cubic system, the change in relative dielectric constant in the temperature range of −55 to 125 ° C. becomes flat, and the hysteresis in the electric field-dielectric polarization characteristics becomes small. . Therefore, it is possible to obtain a dielectric ceramic having a small relative dielectric constant change rate despite having a relative dielectric constant of 410 or more.

  That is, in the dielectric ceramic according to the present invention, the crystal particles are formed by dissolving calcium, magnesium, rare earth elements and manganese in barium titanate, refining the average particle size, and making the crystal structure cubic. The temperature characteristic of dielectric constant can be flattened.

  It should be noted that the phase transition phenomenon is changed by containing a predetermined amount of magnesium, rare earth element and manganese, and the curve showing the change rate of the relative dielectric constant has two peaks centering on room temperature in the temperature range of -55 ° C to 125 ° C. It has become.

  That is, in the dielectric ceramic according to the present invention, a part of barium in barium titanate is replaced with calcium having a small ionic radius, so that the phase transition point moves to the high temperature side and the relative permittivity is flat with respect to the temperature. Improves. The introduction of calcium increases the solid solubility of magnesium, rare earth elements, and manganese, thereby lowering the phase transition temperature of the paraelectric phase to the ferroelectric phase, and at the same time becoming diffuse and stabilizing the temperature characteristics of the relative permittivity. It is considered to be.

  That is, when the crystal structure of the crystal grains constituting the dielectric ceramic is cubic, the spontaneous polarization due to ion displacement can be suppressed and the ferroelectricity can be suppressed, and thus a curve indicating the change in relative permittivity with respect to temperature is −55. It is thought that it will have two peaks in the temperature range of deg.

In the dielectric ceramic of the present invention, as described above, calcium is 0.1 mol or less in terms of CaO and 0.01 to 0.064 mol in terms of MgO with respect to 1 mol of titanium constituting barium titanate. It is important to contain rare earth elements in the range of 0.0015 to 0.03 mol in terms of RE ₂ O ₃ and manganese in the range of 0.0002 to 0.03 mol in terms of MnO.

This is because the content of calcium per 1 mol of titanium is more than 0.1 mol in terms of CaO, magnesium is more than 0.064 mol in terms of MgO, or rare earth elements are more than 0.03 in terms of RE ₂ O ₃ In contrast, when the relative dielectric constant is decreased, the ratio of the dielectric ceramic is reduced when magnesium is less than 0.01 mol in terms of MgO or rare earth elements are less than 0.0015 mol in terms of RE ₂ O _3. This is because the rate of change of the dielectric constant increases. Also, if manganese is less than 0.0002 mol in terms of MnO, the dielectric ceramic after firing is reduced and the insulation resistance of the dielectric ceramic is reduced, so that it has no function, and manganese is in terms of MnO. It is because there exists a malfunction that a dielectric constant will fall when it exceeds 0.03 mol.

  In addition, in the dielectric ceramic of the present invention, it is important that the average particle diameter of crystal grains constituting the dielectric ceramic is 80 to 200 nm in order to exhibit the temperature characteristic of the flat relative dielectric constant as described above. is there. This is because the relative dielectric constant decreases when the average crystal grain size of the crystal particles is smaller than 80 nm, while the temperature coefficient of the relative dielectric constant increases when the average crystal grain size of the crystal particles is larger than 200 nm. Because it becomes. This is because when the average crystal grain size of crystal grains is larger than 200 nm, tetragonal crystals having a perovskite crystal structure of barium titanate may be generated in the dielectric ceramic.

  That is, when the average crystal grain size of the crystal grains increases, the dielectric constant increases because the number of phases exhibiting ferroelectricity increases in the dielectric ceramic, but the temperature coefficient of the relative permittivity increases and spontaneous polarization appears. This is due to the formation of tetragonal and tetragonal phases in the crystal structure identified by X-ray diffraction of dielectric ceramics. When a capacitor having such a dielectric ceramic as a dielectric layer is used on a power supply circuit, a “sounding” phenomenon due to an electrostriction phenomenon is likely to occur.

In the dielectric ceramic according to the present invention, as a more preferable composition and particle size, the calcium content is 0.025 to 0.075 mol in terms of CaO, and the magnesium content is 0.01 to 0.04 in terms of MgO. Mole, rare earth element is 0.0015 to 0.03 mol in terms of RE ₂ O ₃ and manganese is 0.0002 to 0.03 mol in terms of MnO, and the average grain size of crystal grains is 130 to 200 nm The dielectric ceramic in this range can have a relative dielectric constant of 690 or more at 25 ° C. and a change rate of the relative dielectric constant of −55 to 125 ° C. within ± 10%. In the dielectric ceramic according to the present invention, when such a composition and particle size are determined, the relative dielectric constant at 25 ° C. is lower than 1000, and the change rate of the relative dielectric constant at −55 to 125 ° C. is ± 10%. If it is within the range, the polarization value can be 0.03 μC / cm ² or less.

  The average grain size of the dielectric ceramic crystal particles is determined by polishing the fracture surface of the dielectric ceramic, taking a picture of the internal structure using a scanning electron microscope, and then displaying the crystal grains shown in the photograph. The contour of the image is processed, and the diameter of the circle is obtained from the area of each particle and averaged.

  The crystal structure of the dielectric ceramic is identified by measuring 2θ at 10 to 100 ° using X-ray diffraction using Cukα as a tube. In this case, a powder obtained by pulverizing a dielectric ceramic is used as a sample, and a cubic system and a tetragonal system are evaluated from diffraction lines of (002) plane and (200) plane based on JCPDS data of barium titanate. In the cubic system, (002) (200) diffraction lines are not separated, and in the tetragonal system, diffraction peaks appear on both sides of the cubic (002) (200) diffraction lines, Alternatively, it is assumed that diffraction peaks are separated.

  In the present invention, the crystal structure mainly composed of a cubic system means a state in which the diffraction peak intensity of the (110) plane, which is the strongest peak of cubic barium titanate, is larger than the diffraction peak intensity of a different phase. .

Next, a method for manufacturing the dielectric ceramic according to the present invention will be described. First, BaCO ₃ powder having a purity of 99% or more, CaCO ₃ powder, TiO ₂ powder, MgO powder, Y ₂ O ₃ powder and manganese carbonate powder are used as the raw material powder. These raw material powders are composed of CaCO ₃ at a ratio of 0.10 mol or less (excluding zero) and MgO at a ratio of 0.01 to 0.064 mol with respect to 1 mol of titanium constituting barium titanate. Y ₂ O ₃ is blended in a proportion of 0.0015 to 0.03 mol, and MnO is blended in a proportion of 0.0002 to 0.03 mol.

  Next, the above mixture of raw material powders is wet-mixed and dried, and then calcined at a temperature of 900 to 1100 ° C. and pulverized. It is important that the average particle size of the calcined powder after pulverization is 100 nm or less in order to make the crystal structure mainly composed of a cubic system at the stage of the calcined powder.

  The calcining temperature is set to 900 ° C. or higher in order to produce a cubic crystal phase mainly composed of barium titanate in the calcined powder, and the temperature is set to 1100 ° C. or lower in the next step. This is to maintain the reactivity at the time and to prevent the particle size from becoming coarse during calcination.

  The crystal structure of the calcined powder is also identified by the X-ray diffraction method described above. The average particle size of the calcined powder is measured in a state where the calcined powder is dispersed on the sample stage. That is, the crystal structure of the calcined powder is also identified by measuring 2θ at 10 to 100 ° using X-ray diffraction using Cukα as a tube. In this case, a powder obtained by pulverizing the calcined powder is used as the sample, and the crystal structure is identified by the same method as the evaluation method for the dielectric ceramic based on the JCPDS data of barium titanate.

  Next, the pulverized calcined powder is molded into a predetermined shape and fired by a hot press method at a temperature range of 1050 to 1250 ° C. to obtain a densified dielectric ceramic. In this case, the hot press method uses a carbon mold and is heated under pressure in a nitrogen atmosphere under a pressure of 80 to 150 MPa.

  The firing temperature is set to 1050 ° C. for the purpose of densifying the dielectric ceramic. On the other hand, setting the firing temperature to 1250 ° C. or lower suppresses the grain growth of crystal grains and reduces excessive reduction of the dielectric ceramic. This is to suppress the decomposition of the crystal phase.

  By sintering using a cubic powder as the calcined powder in this way, it becomes easy to realize a cubic crystal structure even in the sintered body, and this makes the dielectric constant close to paraelectricity. Therefore, it is possible to easily form a dielectric ceramic having a high dielectric constant while maintaining the temperature characteristic of the dielectric constant.

  FIG. 1 is a schematic cross-sectional view showing a capacitor of the present invention. The following capacitor can be formed using the dielectric ceramic of the present invention.

  The capacitor of the present invention is provided with an external electrode 12 at the end of the capacitor body 10. The capacitor body 10 is configured by alternately laminating dielectric layers 13 and conductor layers 14 as internal electrode layers. Here, it is important that the dielectric layer 13 is formed by the above-described dielectric ceramic of the present invention. The conductive layer 14 is preferably a base metal such as Ni or Cu in that the manufacturing cost can be suppressed even if the conductor layer 14 is highly laminated, and in particular, Ni is intended to be simultaneously fired with the dielectric layer 13 constituting the capacitor of the present invention. More desirable. The conductor layer 14 preferably has an average thickness of 1 μm or less.

  Further, when producing such a capacitor, the above mixed powder is formed into a green sheet, and a conductor paste to be a conductor layer 14 is prepared and printed on the surface of the green sheet, and then laminated and fired. The laminated body 1 is formed. Thereafter, a conductor paste is further printed on the end face of the laminate 1 and fired to form the external electrode 12, whereby a capacitor can be obtained. Since the capacitor thus obtained uses the above-mentioned dielectric ceramic as a dielectric layer, the “sounding” phenomenon caused by the electrostriction phenomenon can be suppressed when used on a power supply circuit.

The dielectric ceramic according to the present invention was produced as follows. First, prepare BaCO ₃ powder, CaCO ₃ powder, TiO ₂ powder, MgO powder, Y ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ oxide powder, and manganese carbonate powder each having a purity of 99.9%. The mixed powder was prepared by mixing at the ratio shown in Table 1. The amount shown in Table 1 is an amount corresponding to the oxide equivalent amount of the element.

  Next, the mixed powder was calcined at a temperature of 1050 ° C. for 2 hours, and the calcined powder was pulverized. At this time, the average particle size of the calcined powder after pulverization was set in the range of 50 to 150 nm. Thereafter, the calcined powder was formed into a pellet having a diameter of 12 mm and a thickness of 1 mm.

  Next, a plurality of pellets of each composition were fired. The firing temperature was 1050 to 1250 ° C. Firing was performed by hot pressing in a nitrogen atmosphere using a nitrogen atmosphere. The hot press pressure was 100 MPa, and a carbon mold was used as a hot press jig. An indium gallium conductor film was printed on the surface of the sample after firing.

  These samples, which are dielectric porcelains, were measured for capacitance using a LCR meter 4284A at a frequency of 1.0 kHz and an input signal level of 1.0 V. From the diameter and thickness of the sample and the area of the conductor film, the dielectric constant was measured. The rate was calculated. The number of samples was 10 each.

  Moreover, the change rate of the dielectric constant was measured in the range of −55 to 125 ° C. The maximum value on the + side in Table 1 is the ratio of the highest relative dielectric constant when 25 ° C. is the reference in the temperature range, while the maximum value on the − side is the lowest relative dielectric constant when the 25 ° C. is the reference. It is a percentage of the rate.

  The average crystal grain size of the dielectric ceramic crystal grains is obtained by polishing the fracture surface of the obtained dielectric ceramic, then taking a picture of the internal structure using a scanning electron microscope, and then the crystals shown in the picture The particle outline was image-processed, and each particle was assumed to be a circle and its diameter was obtained and averaged. The magnification of the photograph was about 30000 times, and the number of observation points was 3 for each sample. The calcined powder was obtained by the same method by dispersing the calcined powder on a sample stage for a scanning electron microscope.

  The crystal structure of the dielectric ceramic was measured by using X-ray diffraction with Cukα as a tube and once pulverizing the obtained dielectric ceramic and setting 2θ to 10 to 100 °. In this case, the cubic system was evaluated from the diffraction lines of the (002) plane and the (200) plane based on the JCPDS data of barium titanate. In the cubic system, diffraction lines on the (002) plane and (200) plane were not separated. The same measurement was performed on the calcined powder. In the examples, both the calcined powder and the fired dielectric ceramic were mainly composed of a cubic system.

  Moreover, the magnitude | size of the piezoelectric distortion was calculated | required by the measurement of dielectric polarization about the obtained dielectric ceramic. The magnitude of the piezoelectric strain is determined by the electrostriction constant, the relative permittivity, and the magnitude of the spontaneous polarization, and particularly depends on the magnitude of the polarization. Therefore, the magnitude of the polarization (polarization value) is an index of the magnitude of the piezoelectric strain. It was. In this case, an electric field-polarization history curve was measured when an AC voltage having a frequency of 10 Hz with an electric field strength of 2 V / μm was applied, and the charge amount (residual polarization) at 0 V in the electric field-polarization history curve was evaluated. .

  In addition, the composition analysis of the obtained sintered body sample was performed by ICP analysis or atomic absorption analysis. In this case, the obtained dielectric porcelain mixed with boric acid and sodium carbonate and dissolved in hydrochloric acid is first subjected to qualitative analysis of the elements contained in the dielectric porcelain by atomic absorption spectrometry, and then specified. The diluted standard solution for each element was used as a standard sample and quantified by ICP emission spectroscopic analysis. Further, the amount of oxygen was determined using the valence of each element as the valence shown in the periodic table.

Table 1 shows the prepared composition, calcining conditions and firing conditions, and Table 2 shows the composition, average crystal grain size and characteristics of the crystal grains in the sample after firing.

The obtained dielectric porcelain is a reduced sample no. It was the sample which can be evaluated except for 15. As is clear from the results in Table 2, the dielectric ceramic of the present invention had a relative dielectric constant of 410 or more at 25 ° C. and a change rate of the relative dielectric constant within −10% within a range of −55 to 125 ° C. Further, it was confirmed that the sample had a polarization value of 0.1 μC / cm ² or less and a small piezoelectric strain.

The calcium content is 0.025 to 0.075 mol in terms of CaO, the magnesium content is 0.01 to 0.04 mol in terms of MgO, and the rare earth element is 0.0015 to in terms of RE ₂ O _3. 0.03 mol and manganese are 0.0002 to 0.03 mol in terms of MnO, and the average crystal grain size of the crystal particles is preferably 130 to 200 nm. The dielectric ceramic in this range has a ratio at 25 ° C. The dielectric constant was 690 or more, and the rate of change of the relative dielectric constant at −55 to 125 ° C. was within ± 10%. Among them, a sample having a relative dielectric constant at 25 ° C. of 1000 or less and a change rate of the relative dielectric constant at −55 to 125 ° C. within ± 10% has a polarization value of 0.03 μC / cm ² or less, and is further piezoelectric. The distortion was small.

  On the other hand, in the sample having an average grain size larger than 0.20 μm, the relative dielectric constant at 25 ° C. was as large as 1000 or more. However, tetragonal strain was confirmed in X-ray diffraction, and the change in the relative dielectric constant. The rate was + 28% or more in the range of −55 to 125 ° C., which was larger than that of the sample of the present invention. In the sample having an average grain size of smaller than 0.08 μm, the relative dielectric constant at 25 ° C. was 360 or less.

  In addition, even in the samples in which the contents of calcium, magnesium, rare earth elements, and manganese were outside the scope of the present invention, the relative dielectric constant was low or the temperature change rate of the relative dielectric constant was large.

  Hereinafter, actual examples will be described in more detail. FIG. 2 is a graph showing (a) temperature change and (b) temperature change rate (based on a value of 25 ° C.) of the relative dielectric constant of the dielectric ceramic of the present invention.

The curve with # 10 in the graph is Sample No. which is an example of the dielectric ceramic of the present invention. The curves marked with No. 10 and # 2 are sample Nos. Which are comparative examples of the present invention. This is the case of 2.

  Sample No. which is a curve marked with # 10. In the dielectric ceramic of No. 10, when the barium titanate contains a predetermined amount of the above-described elements, the phase transition peak originally present at room temperature and around 125 ° C. of barium titanate moves to the low temperature side and becomes diffused. Furthermore, by controlling the grain size of the crystal grains, the dielectric constant in the ground state of the material is surfaced, and shows two maxima in the temperature change of the dielectric constant. Unlike the normal monotonous temperature change, a flat temperature characteristic is obtained. It is done. In addition, the phase transition is diffused and the ferroelectricity is suppressed by size control, so that paraelectric characteristics are easily developed.

In the present invention, the rate of change of the relative dielectric constant depends on the amount of magnesium rather than the rare earth element or manganese, but a dielectric ceramic containing barium titanate as a main component and containing magnesium (see Non-Patent Document 1). As described above, merely replacing Ti in BaTiO ₃ with Mg does not lower the phase transition point and make the phase transition diffuse. In the present invention, in particular, it is considered that the above-mentioned dielectric characteristics are manifested by simultaneously dissolving the rare earth element into the crystal grains.

  On the other hand, sample No. which is a comparative example. 2, the fundamental dielectric properties do not change greatly with grain growth as seen at room temperature or below, but at high temperatures, the characteristics of the phase transition of Ca-containing barium titanate are surfaced by grain growth, and are around 100 ° C. As a result, the dielectric constant increases, and the dielectric ceramic has a large change rate of the relative permittivity.

Non-Patent Document 1 includes Toru Nagai, Kenji Iijima, Hae Jin Hwang, Mutsuo Sando, Toru Sekino (
Tohru Sekino), Koichi-Niihara (koichi Niihara), EFFECT OF · MgO · doping-on-the-Phase Transformation Of _{· BaTiO 3 (Effect of MgO Doping} on the Phase transformation of BaTiO 3) Journal of American of the Ceramic Society (2000) 83 [1] p. 107-112.

It is a cross-sectional schematic diagram which shows the example of the capacitor | condenser of this invention. It is a graph which shows (a) temperature change of the dielectric constant about the dielectric material ceramic of this invention, and (b) temperature change rate (on the basis of the value of 25 degreeC).

Explanation of symbols

13. ・ Dielectric layer 14 ・ ・ Conductive layer

Claims (3)

A dielectric ceramic composed mainly of barium titanate and comprising crystal grains containing calcium, magnesium, rare earth elements, and manganese, and a grain boundary phase, with respect to 1 mole of titanium constituting the barium titanate, Is 0.1 to 0.064 mol in terms of CaO, magnesium is 0.01 to 0.064 mol in terms of MgO, rare earth elements are 0.0015 to 0.03 mol in terms of RE ₂ O ₃ , and manganese is 0.000 in terms of MnO. The crystal structure is contained in a range of 0002 to 0.03 mol, and the crystal structure identified by X-ray diffraction of the dielectric ceramic is mainly composed of a cubic system, and the average crystal grain size of the crystal grains Is a dielectric porcelain characterized by a thickness of 80 to 200 nm. The calcium content is 0.025 to 0.075 mol in terms of CaO, the magnesium content is 0.01 to 0.04 mol in terms of MgO, and the average grain size of the crystal grains is 130 to The dielectric ceramic according to claim 1, wherein the dielectric ceramic is 200 nm. A capacitor comprising a dielectric layer made of the dielectric ceramic according to claim 1 and a conductor layer.

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