JP2009292678A - Dielectric ceramic and capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric ceramic exhibiting a high permittivity and the stable temperature characteristic of the relative permittivity and to provide a capacitor using the same. <P>SOLUTION: The dielectric ceramic has crystal grains containing barium titanate as a principal element and grain boundary phases formed among the crystal grains and contains magnesium, at least one rare earth element (RE) selected from among gadolinium, terbium, dysprosium, holmium, erbium and ytterbium, and manganese each in a fixed ratio to 1 mol barium constituting barium titanate expressed in terms of oxide, wherein lutetium is contained in a fixed ratio to 100 pts.mass barium titanate expressed in terms of oxide and the average particle diameter of the crystal grains is 0.05-0.2 μm. The capacitor having high capacitance and stable temperature coefficient of capacitance is formed by applying the dielectric ceramic as a dielectric layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  At present, digital electronic devices such as mobile computers and mobile phones are rapidly spreading, 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 which are receivers for digital terrestrial broadcasting, and many LSIs are used for these digital electronic devices.

For this reason, many bypass capacitors are mounted on power supply circuits that constitute these digital electronic devices such as liquid crystal displays and plasma displays. The capacitor used here is a multilayer ceramic capacitor having a high dielectric constant (for example, see Patent Document 1) when a high capacitance is required. On the other hand, when temperature characteristics are regarded as important even with a low capacity, a temperature compensation type multilayer ceramic capacitor having a small capacity change rate (for example, see Patent Document 2) is employed.
JP 2002-89231 A Japanese Patent Laid-Open No. 2002-294481

  However, in the high dielectric constant multilayer ceramic capacitor disclosed in Patent Document 1, the dielectric layer is composed of crystal grains of dielectric ceramic having ferroelectricity, so that the temperature change rate of the relative dielectric constant is large. In addition, there is a problem that the hysteresis in the electric field-dielectric polarization characteristics is large.

  In addition, a capacitor in which the dielectric layer disclosed in Patent Document 1 is formed using a ferroelectric dielectric ceramic is likely to generate noise noise due to electrically induced distortion on a power supply circuit. This property has been an obstacle when used for plasma displays.

  On the other hand, the temperature compensation type monolithic ceramic capacitor has a small hysteresis in the electric field-dielectric polarization characteristics because the dielectric ceramic constituting it is paraelectric. For this reason, although there is an advantage that the electric induction strain peculiar to the ferroelectricity does not occur, there is a problem that the capacity as a bypass capacitor is not satisfied because the dielectric constant of the dielectric ceramic is low and the storage capacity is low.

  An object of the present invention is to provide a dielectric ceramic exhibiting a temperature characteristic of a high dielectric constant and a stable relative dielectric constant, and a capacitor using the dielectric ceramic.

The dielectric ceramic of the present invention is a dielectric ceramic comprising crystal grains mainly composed of barium titanate and a grain boundary phase formed between the crystal grains, and the barium 1 constituting the barium titanate. 0.01 to 0.06 mol of magnesium in terms of MgO with respect to mol, and at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium in terms of REO _3/2 0.0007 to 0.03 mol and manganese in an amount of 0.0002 to 0.03 mol in terms of MnO, and lutetium to 3.6 in terms of Lu ₂ O ₃ with respect to 100 parts by mass of the barium titanate. ˜52.1 parts by mass, and the average particle size of the crystal particles is 0.05 to 0.2 μm.

Further, in the dielectric ceramic according to the present invention, the magnesium is 0.017 to 0.023 mol in terms of MgO and the rare earth element (RE) is REO _3/2 with respect to 1 mol of barium constituting the barium titanate. While containing 0.0015 to 0.01 mol in terms of conversion and 0.01 to 0.013 mol in terms of MnO, the lutetium is 6 in terms of Lu ₂ O ₃ with respect to 100 parts by mass of the barium titanate. It is desirable that the titanium ratio is 0.97 to 0.98 with respect to 1 mol of barium, which is contained in an amount of .3 to 15.6 parts by mass.

  In addition, the capacitor of the present invention is characterized in that it is composed of a laminate of a dielectric layer made of the dielectric ceramic and a conductor layer.

  Note that the rare earth element RE is based on the rare earth element English representation (Rare earth) in the periodic table.

  According to the dielectric porcelain of the present invention, the temperature change rate of the relative permittivity is smaller than that of the conventional dielectric porcelain, and is higher than that of the conventional dielectric porcelain. In addition, the temperature characteristics of the dielectric constant can be reduced and the spontaneous polarization can be reduced.

  According to the capacitor of the present invention, by applying the dielectric ceramic as the dielectric layer, it is possible to form a capacitor having higher capacity and more stable capacitance-temperature characteristics than the conventional capacitor. Therefore, when this capacitor is used in a power supply circuit, it is possible to suppress the generation of noise noise caused by electrically induced distortion.

The dielectric ceramic of the present invention comprises barium titanate as a main component, magnesium, at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium, and manganese. , Lutetium, and the content thereof is selected from 0.01 to 0.06 mol of magnesium in terms of MgO with respect to 1 mol of barium, gadolinium, terbium, dysprosium, holmium, erbium and ytterbium. And at least one rare earth element (RE) converted to 0.0007 to 0.03 mol in terms of REO _3/2 and 0.0002 to 0.03 mol in terms of manganese to MnO, and 100 parts by mass of the barium titanate On the other hand, lutetium in terms of Lu ₂ O ₃ is 3. Contains 6 to 52.1 parts by mass.

  In the dielectric ceramic according to the present invention, it is important that the average grain size of crystal grains constituting the dielectric ceramic is 0.05 to 0.2 μm.

When the dielectric ceramic is in the above composition and particle size range, the relative dielectric constant at room temperature (25 ° C.) described later is 180 or more, the relative dielectric constant at 125 ° C. is 160 or more, and the relative dielectric constant between 25 ° C. and 125 ° C. Temperature coefficient (ε ₁₂₅ −ε ₂₅ ) / (ε ₂₅ (125-25)) can be made to be 1000 × 10 ⁻⁶ / ° C. or less in absolute value, and a dielectric ceramic with small hysteresis in electric field-dielectric polarization characteristics can be formed. .

  Such a dielectric ceramic of the present invention includes barium titanate, magnesium, at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium, manganese, and lutetium. Is a solid solution. In addition, by making the average particle size of the crystal particles mainly composed of barium titanate in which these components are dissolved into a range of 0.05 to 0.2 μm, the crystal structure of the crystal particles is mainly cubic. It can be said that. As a result, the ferroelectricity due to the tetragonal crystal structure is lowered, the paraelectricity can be increased, and the spontaneous polarization can be reduced by increasing the paraelectricity.

  In addition, by making the crystal structure of the crystal grains mainly composed of barium titanate into a crystal structure mainly composed of a cubic system, a curve indicating a change rate of relative permittivity is in a temperature range of −55 ° C. to 125 ° C. In both cases, the hysteresis in the electric field-dielectric polarization characteristics becomes small. Therefore, even when the relative dielectric constant is 180 or more, a dielectric ceramic having a small relative dielectric constant temperature coefficient can be obtained.

  That is, a predetermined amount of magnesium, at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium and manganese are contained in the above-mentioned range with respect to barium titanate. Thus, a dielectric ceramic exhibiting a Curie temperature of 25 ° C. or more and a positive temperature coefficient of relative dielectric constant is obtained, and lutetium is further added to the dielectric ceramic exhibiting such dielectric characteristics. In this case, a greater effect can be obtained, and the temperature characteristic can be flattened by reducing the temperature coefficient of the relative dielectric constant. In this case, the curve indicating the change rate of the relative dielectric constant has two peaks centering on 25 ° C. in the temperature range of −55 ° C. to 125 ° C.

Here, lutetium has a function of suppressing the coarsening of crystal grains mainly composed of barium titanate, and 3.6 to 52.1 in terms of Lu ₂ O ₃ with respect to 100 parts by mass of barium titanate. It is important to contain part by mass.

That is, when the content of lutetium with respect to 100 parts by mass of barium titanate is less than 3.6 parts by mass in terms of Lu ₂ O ₃ , the dielectric ceramic has a high relative dielectric constant, but has a large relative dielectric constant temperature coefficient. It becomes. On the other hand, when the content of lutetium with respect to 100 parts by mass of barium titanate is more than 52.1 parts by mass in terms of Lu ₂ O ₃ , the relative dielectric constant at 25 ° C. becomes lower than 180, and the relative dielectric constant at 125 ° C. This is because the rate is less than 160.

In addition, the content of magnesium, manganese, and at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium is magnesium in terms of MgO with respect to 1 mol of barium. 0.01 to 0.06 mol, at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium in an amount of 0.0007 to 0.03 mol in terms of REO _3/2 , Manganese is contained in an amount of 0.0002 to 0.03 mol in terms of MnO.

  That is, when the content of magnesium with respect to 1 mol of barium is less than 0.01 mol or more than 0.06 mol in terms of MgO, the temperature coefficient of the dielectric constant of the dielectric ceramic increases.

Further, the content of at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium and erbium with respect to 1 mol of barium is less than 0.0007 mol in terms of RE ₂ O ₃ , or 0 When the amount is more than 0.03 mole, the dielectric constant of the dielectric ceramic is high, but the temperature coefficient of the relative permittivity becomes large. Furthermore, when the manganese content relative to 1 mol of barium is less than 0.0002 mol or more than 0.03 mol in terms of MnO, the temperature coefficient of the dielectric constant of the dielectric ceramic becomes large.

  The rare earth element (RE) contained in the dielectric ceramic is at least one of holmium and erbium in that the relative dielectric constant at room temperature (25 ° C.) can be increased to 250 or higher, and the dielectric constant can be increased. The rare earth element (RE) is more preferable.

  Furthermore, in the dielectric ceramic according to the present invention, the average particle diameter of crystal grains mainly composed of barium titanate is 0.05 to 0.2 μm.

  That is, by setting the average particle size of the crystal particles mainly composed of barium titanate to 0.05 to 0.2 μm, the crystal particles mainly composed of cubic system of the crystal particles mainly composed of barium titanate. Thus, the hysteresis in the electric field-dielectric polarization characteristic is small and the characteristic close to paraelectricity can be obtained.

  On the other hand, when the average particle diameter of the crystal grains mainly composed of barium titanate is smaller than 0.05 μm, the contribution of orientation polarization is lost, so that the dielectric constant of the dielectric ceramic is lowered. On the other hand, when the average particle size of the crystal particles is larger than 0.2 μm, a tetragonal crystal phase is observed in the measurement by X-ray diffraction, and the temperature coefficient of the dielectric constant of the dielectric ceramic becomes large.

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

And as a preferable range of the composition of the above components contained in the dielectric ceramic of the present invention, magnesium with respect to 1 mol of barium is 0.017 to 0.023 mol in terms of MgO, gadolinium, terbium, dysprosium, holmium, erbium. And at least one rare earth element (RE) selected from ytterbium is 0.0015 to 0.01 mol in terms of REO _3/2 , manganese is 0.01 to 0.013 mol in terms of MnO, and barium titanate It is preferable that lutetium is in the range of 6.3 to 15.6 parts by mass in terms of Lu ₂ O _{5 with} respect to 100 parts by mass and the titanium ratio with respect to 1 mol of barium is 0.97 to 0.98. The average particle size of the crystal particles is more preferably 0.14 to 0.18 μm.

For dielectric ceramics in these ranges, the relative dielectric constant at 25 ° C. should be 420 or more, the relative dielectric constant at 125 ° C. should be 400 or more, and the temperature coefficient of relative dielectric constant should be 573 × 10 ⁻⁶ / ° C. or less in absolute value. And a polarization charge showing hysteresis of dielectric polarization can be reduced to 40 nC / cm ² or less at 0V.

  Here, the average particle diameter of the crystal particles mainly composed of barium titanate is determined by polishing the fracture surface of a sample made of a dielectric ceramic after firing and then using a scanning electron microscope. Take a picture of the tissue, draw a circle with 50 to 100 crystal grains on the picture, select the crystal grains that fall within and around the circle, image the outline of each crystal grain, Obtain the area, calculate the diameter when replaced with a circle with the same area, and obtain the average value.

In addition, the relative dielectric constant at 25 ° C. and 125 ° C. is determined by using a LCR meter 4284A to obtain a sample made of a dielectric ceramic that is formed into a predetermined pellet shape and has a conductor film formed on the surface. This is a value calculated from the diameter and thickness of the pellet-shaped sample and the area of the conductor film by measuring the capacitance at 1.0 kHz, input signal level 1.0 V, temperature 25 ° C. and 125 ° C. The temperature coefficient of the relative permittivity between 25 ° C. and 125 ° C. is the relative permittivity at 25 ° C. and 125 ° C. [(ε ₁₂₅ −ε ₂₅ ) / (ε ₂₅ (125-25)) ε ₂₅ : 25 ° C., respectively. Relative dielectric constant at ε ₁₂₅ : relative dielectric constant at 125 ° C.].

  Next, a method for manufacturing the dielectric ceramic according to the present embodiment will be described.

First, BaCO ₃ powder, TiO ₂ powder, MgO powder, Gd ₂ O ₃ powder, Tb ₂ O ₃ powder, Dy ₂ O ₃ powder, Ho ₂ O having a purity of 99% or more as raw material powders. _At least one rare earth element (RE) oxide powder selected from _three powders, Er ₂ O ₃ powder and Yb ₂ O ₃ powder, and manganese carbonate (MnCO ₃ ) powder are used. These raw material powders are 0.01 to 0.06 mol of MgO, Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O _{3 with} respect to 1 mol of barium constituting barium titanate. , Er ₂ O ₃ and Yb ₂ O ₃ at least one rare earth element (RE) oxide in terms of REO _3/2 is 0.0007 to 0.03 mol, and MnCO ₃ is 0.0002 to 0.00. Each is blended at a ratio of 03 moles.

  Next, the mixture of the raw material powders described above is wet-mixed and dried, and then calcined at a temperature of 900 to 1100 ° C. to prepare a calcined powder, and the calcined powder is pulverized. At this time, a dielectric ceramic having a high dielectric constant that maintains temperature characteristics of a dielectric constant close to paraelectricity by growing grains so that the crystal structure of the calcined powder is mainly composed of a cubic system. Can be obtained.

  The average particle size of the calcined powder is preferably 0.04 to 0.1 μm. Thereby, in the calcined powder, the expression of ferroelectricity can be suppressed. The average particle diameter of the calcined powder is, as will be described later, the calcined powder dispersed on an electron microscope sample stage, photographed with a scanning electron microscope, and the contour of the calcined powder displayed in the photograph The image is processed, a circle containing 50 to 100 crystal particles is drawn on the photograph, the powder applied to the inside and the circumference of the circle is selected, the contour of each powder is image-processed, and the area of each powder is obtained. Calculate the diameter when the diameter is replaced with a circle having the same area, and obtain the average value.

Then mixed at a ratio of 3.5 to 50 parts by weight of the _Lu 2 _{O 3} powder with respect to the calcined powder 100 parts by weight. Thereafter, the mixed powder was formed into pellets, it is possible to obtain a dielectric ceramic of the present invention by performing the firing at a temperature range of 1300 ° C. to 1400 ° C. in H ₂ -N _2. Here, when the firing temperature is lower than 1300 ° C., the grain growth and densification of crystal grains are suppressed, so that the density of the dielectric ceramic becomes low. On the other hand, if the firing temperature is higher than 1400 ° C., the crystal grains of the dielectric ceramic may grow too much.

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

  As shown in FIG. 1, the capacitor of the present invention is one in which external electrodes 12 are provided at both ends of a capacitor body 10. The capacitor body 10 is composed of a laminated body in which a plurality of dielectric layers 13 and a plurality of conductor layers 14 as internal electrode layers are alternately laminated. It is important that the dielectric layer 13 is formed of the above-described dielectric ceramic of the present invention. That is, as the dielectric layer 13, by applying the above dielectric ceramic exhibiting a high dielectric constant and a stable relative dielectric constant temperature characteristic and having a small spontaneous polarization, the capacitance is higher than that of the conventional capacitor and the capacitance temperature characteristic is more stable. It becomes a simple capacitor. For this reason, when this capacitor is used in a power supply circuit, it is possible to suppress the generation of noise noise caused by electrically induced distortion.

  The thickness of the dielectric layer 13 is desirably 1 to 30 μm. In particular, when the thickness of the dielectric layer 13 is 5 μm or less, there is an advantage that the capacitance of the capacitor can be increased by thinning the dielectric layer 13.

  The conductor 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 more particularly Ni is more preferable in terms of simultaneous firing with the dielectric layer 13. The thickness of the conductor layer 14 is preferably 1 μm or less on average.

  When producing such a capacitor, first, the above-mentioned mixed powder is formed into a green sheet. Next, a conductor paste to be the conductor layer 14 is prepared, printed on the surface of the green sheet, laminated, and fired to form the laminate 1. Thereafter, a conductor paste is further printed on both end faces of the laminate 1 and fired to form the external electrode 12, whereby the capacitor of the present invention can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example.

[Example 1]
The evaluation sample was produced as follows. First, BaCO ₃ powder, TiO ₂ powder, MgO powder, Gd ₂ O ₃ powder, and MnCO ₃ powder each having a purity of 99.9% were prepared and mixed at a ratio shown in Table 1 to prepare a mixed powder. The amounts of magnesium (Mg), gadolinium (Gd) and manganese (Mn) shown in Table 1 are amounts corresponding to MgO, GdO _3/2 and MnCO ₃ , respectively. Titanium (Ti) is a molar ratio with respect to 1 mole of barium (Ba).

  Next, after calcining the mixed powder prepared above at a temperature of 1000 ° C. to prepare a calcined powder, the calcined powder obtained was pulverized to obtain a calcined powder having an average particle size shown in Table 1. Obtained. The average particle size of the calcined powder is obtained by dispersing the obtained calcined powder on a sample stage for an electron microscope, taking a picture with a scanning electron microscope, and performing image processing on the outline of the calcined powder displayed in the photograph. Then, draw a circle containing 50 to 100 calcined powders on the photograph, select the powder that falls within and around the circle, image the outline of each powder, find the area of each powder, and the same The diameter when replaced with a circle having an area was calculated and obtained from the average value.

Thereafter, Lu ₂ O ₃ powder having a purity of 99.9% was mixed at a ratio shown in Table 1 with respect to 100 parts by mass of the calcined powder. This mixed powder was granulated and formed into pellets having a diameter of 16.5 mm and a thickness of 1 mm.

Next, 10 pellets of each composition were fired at a temperature shown in Table 1 in H ₂ —N ₂ to obtain a dielectric ceramic as a sample. The average particle diameter of the crystal particles mainly composed of barium titanate was determined as follows. First, the fracture surface of the fired sample was roughly polished using # 1200 abrasive paper, then polished with a 3 μm particle size diamond paste applied on a hard buff, and further on a soft buff. A 0.3 μm alumina abrasive grain was applied and finish polishing was performed. Next, after etching with an acidic aqueous solution (hydrochloric acid-hydrogen fluoride), a photograph of the internal structure was taken using a scanning electron microscope. Next, a circle containing 50 to 100 crystal grains is drawn on the photograph, crystal grains covering the circle and the circumference are selected, and the outline of each crystal grain is image-processed to obtain the area of each grain. The diameter when replaced with a circle having the same area was calculated and obtained from the average value.

  An indium gallium conductor layer was printed on the surface of the fired sample to obtain a dielectric property evaluation sample (Sample Nos. 1-1 to 35 in Table 2).

These samples, which are dielectric ceramics, were measured for capacitance using a LCR meter 4284A at a frequency of 1.0 kHz, an input signal level of 1.0 V, temperatures of 25 ° C. and 125 ° C., and the diameter and thickness of the sample. The relative dielectric constants at 25 ° C. and 125 ° C. were calculated from the area of the conductor layer. Further, the temperature coefficient of the relative permittivity is the relative permittivity at 25 ° C. and 125 ° C. The relative permittivity at [(ε ₁₂₅ −ε ₂₅ ) / (ε ₂₅ (125-25)) ε ₂₅ : 25 ° C., respectively. , Ε ₁₂₅ : relative dielectric constant at 125 ° C.]. In these measurements, the number of samples was 10 and the average value was obtained.

  Moreover, the magnitude | size of the electrically induced strain was calculated | required by the measurement of dielectric polarization (polarization charge) about the obtained sample. In this case, the evaluation was based on the value of the charge amount (residual polarization) at 0 V when the voltage was changed in the range of ± 1250 V.

  The composition analysis of the sample was performed by ICP (Inductively Coupled Plasma) analysis or atomic absorption analysis. In this case, the obtained sample is mixed with boric acid and sodium carbonate, and the molten material is dissolved in hydrochloric acid. First, qualitative analysis of the elements contained in the sample is performed by atomic absorption analysis, and then each specified element is analyzed. The diluted standard solution 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 preparation composition, the average particle size of the calcined powder, and the firing temperature. Table 2 shows the average particle size and characteristics of the crystal particles after firing (relative permittivity, absolute value of temperature coefficient of relative permittivity, relative permittivity). The temperature change curve and the polarization charge) result are shown respectively.

Here, the addition amount of Lu ₂ O ₃ in Table 1 is a ratio with respect to 100 parts by mass of the calcined powder. On the other hand, the content of Lu ₂ O ₃ in Table 2 is a ratio with respect to 100 parts by mass of barium titanate in the dielectric ceramic (sample). The amounts of Mg, rare earth element (RE) and Mn shown in Table 2 are oxide equivalent amounts. The “average particle size of crystal particles” in Table 2 means the average particle size of crystal particles mainly composed of barium titanate. “Absolute value of temperature coefficient of relative permittivity” in Table 2 means the absolute value of the average value of the temperature coefficient of relative permittivity obtained above. In Table 2, samples with no two peaks centered around 25 ° C. are marked with ○ in the polarization charge column for those not marked with ○ in the curve of the relative dielectric constant temperature change curve. Those not attached indicate samples whose polarization charge is not less than 40 nC / cm ² .

As is clear from the results in Table 2, the sample No. 1-2 to 1-8, 1-11 to 1-15, 1-18 to 1-21, 1-23 to 1-27, 1-29, 1-30, 1-32, and 1-35, 25 The relative dielectric constant at ° C. was 238 or more, the relative dielectric constant at 125 ° C. was 215 or more, and the temperature coefficient of the relative dielectric constant at 25 to 125 ° C. was 989 × 10 ⁻⁶ / ° C. or less in absolute value.

In particular, with respect to 1 mol of barium, 0.017 to 0.023 mol of MgO, 0.0015 to 0.01 mol of Gd ₂ O ₃ as GdO _3/2 , 0.01 to 0.013 mol of MnO, Sample No. _{2 in which} the content of Lu ₂ O ₃ is 6.3 to 15.6 parts by mass with respect to 100 parts by mass of barium titanate as the main component, and the titanium ratio to 1 mol of barium is 0.97 to 0.98. In 1-4 to 1-6, 1-12 to 1-14, 1-19, 1-20, 1-25 and 1-29, the relative dielectric constant at 25 ° C. is 555 or more, and the relative dielectric constant at 125 ° C. More than 528, the temperature coefficient of relative permittivity is 494 × 10 ⁻⁶ / ° C. or less in absolute value, and the curve showing the change rate of relative permittivity has two peaks in the temperature range of −55 ° C. to 125 ° C. In addition, no large hysteresis was observed in the measurement of electric field-dielectric polarization characteristics. The sample with almost no hysteresis has a polarization charge of 40 nC / cm ² or less at 0V. 2 shows an X-ray diffraction diagram of the dielectric ceramic (sample No. 1-4) obtained in Example 1. FIG. As is clear from FIG. The dielectric ceramic of 1-4 is mainly composed of a cubic crystal structure. Further, other samples within the scope of the present invention also have a crystal structure mainly composed of a cubic system.

In contrast, samples outside the scope of the present invention (Sample Nos. 1-1, 1-9, 1-10, 1-16, 1-17, 1-22, 1-28, 1-31, 1- 33 and 1-34) both had a temperature coefficient of relative permittivity of an absolute value larger than 1000 × 10 ⁻⁶ / ° C.

[Example 2]
Next, a sample was prepared and evaluated in the same manner as in Example 1 except that Gd ₂ O ₃ as an additive component in each composition shown in Example 1 was changed to Tb ₂ O ₃ (Sample No. 1). 2-1 to 2-35).

  Table 3 shows the preparation composition, the average particle size of the calcined powder and the firing temperature, and Table 4 shows the average particle size and characteristics of the crystal particles after firing (relative permittivity, absolute value of temperature coefficient of relative permittivity, relative permittivity The temperature change curve and the polarization charge) result are shown respectively.

The ratio of the content of Lu ₂ O ₃ in the amount and Table 4 Lu ₂ O ₃ in Table 3, the ratio of the same as the proportions shown in each Example 1. Further, the amounts of Mg, rare earth elements (RE) and Mn shown in Table 4 are oxide equivalent amounts as in Example 1. In Table 4, “average particle diameter of crystal grains” and “absolute value of temperature coefficient of relative dielectric constant” have the same meanings as in Example 1. Further, the presence / absence of ◯ in the curve of the temperature change of the relative permittivity shown in Table 4 and the polarization charge column also means the same effect as in Example 1.

As is apparent from the results in Table 4, the sample No. which is the dielectric ceramic of the present invention. 2-2 to 2-8, 2-11 to 2-15, 2-18 to 2-21, 23-23 to 2-27, 2-29, 2-30, 2-32 and 2-35, 25 The relative dielectric constant at ° C. was 243 or more, the relative dielectric constant at 125 ° C. was 220 or more, and the temperature coefficient of the relative dielectric constant at 25 to 125 ° C. was 995 × 10 ⁻⁶ / ° C. or less in absolute value.

Particularly, with respect to 1 mol of barium, MgO is 0.017 to 0.023 mol, Tb ₂ O ₃ is TbO _3/2 and 0.0015 to 0.01 mol, MnO is 0.01 to 0.013 mol, Sample No. _{2 in which} the content of Lu ₂ O ₃ is 6.3 to 15.6 parts by mass with respect to 100 parts by mass of barium titanate as the main component, and the titanium ratio to 1 mol of barium is 0.97 to 0.98. In 2-4 to 2-6, 2-12 to 2-14, 2-19, 2-20, 2-25 and 2-29, the relative dielectric constant at 25 ° C. is 566 or more, and the relative dielectric constant at 125 ° C. More than 540, the temperature coefficient of relative permittivity is 493 × 10 ⁻⁶ / ° C. or less in absolute value, and the curve showing the change rate of relative permittivity has two peaks in the temperature range of −55 ° C. to 125 ° C. In addition, no large hysteresis was observed in the measurement of electric field-dielectric polarization characteristics. The sample with almost no hysteresis has a polarization charge of 40 nC / cm ² or less at 0V. The dielectric ceramics obtained in Example 2 (Sample Nos. 2-2 to 2-8, 2-11 to 2-15, 2-18 to 2-21, 23-23 to 2-27, 2-29, 2-30, 2-32 and 2-35) all have a cubic crystal system as the main component, as in the X-ray diffraction pattern shown in FIG.

In contrast, samples outside the scope of the present invention (Sample Nos. 2-1, 2-9, 2-10, 2-16, 2-17, 2-22, 2-28, 2-31, 2- 33 and 2-34) had a temperature coefficient of relative dielectric constant larger than 1000 × 10 ⁻⁶ / ° C. in absolute value.

[Example 3]
Next, a sample was prepared and evaluated in the same manner as in Example 1 except that Gd ₂ O ₃ as an additive component in each composition shown in Example 1 was changed to Dy ₂ O ₃ (Sample No. 1). 3-1 to 3-35).

  Table 5 shows the prepared composition, the average particle diameter of the calcined powder and the firing temperature, and Table 6 shows the average particle diameter and characteristics of the crystal particles after firing (relative permittivity, absolute value of temperature coefficient of relative permittivity, relative permittivity The temperature change curve and the polarization charge) result are shown respectively.

Here, the added amount of Lu ₂ O ₃ in Table 5 and the ratio of the content of Lu ₂ O ₃ in Table 6 are the same as the ratios shown in Example 1, respectively. Further, the amounts of Mg, rare earth elements (RE) and Mn shown in Table 6 are also equivalent to oxides as in Example 1. In Table 6, “average particle diameter of crystal grains” and “absolute value of temperature coefficient of relative permittivity” have the same meaning as in the first embodiment. Further, the presence / absence of ◯ in the temperature change curve of the dielectric constant and the polarization charge column shown in Table 6 also means the same effect as in Example 1.

As is apparent from the results in Table 6, the sample No. which is the dielectric ceramic of the present invention. 3-2 to 3-8, 3-11 to 15-15, 3-18 to 3-21, 3-23 to 3-27, 3-29, 3-30, 3-32 and 3-35, 25 The relative dielectric constant at 180 ° C. was 180 or more, the relative dielectric constant at 125 ° C. was 162 or more, and the temperature coefficient of the relative dielectric constant at 25 to 125 ° C. was 997 × 10 ⁻⁶ / ° C. or less in absolute value.

In particular, with respect to 1 mol of barium, 0.017 to 0.023 mol of MgO, 0.0015 to 0.01 mol of Dy ₂ O ₃ as DyO _3/2 , 0.01 to 0.013 mol of MnO, Sample No. _{2 in which} the content of Lu ₂ O ₃ is 6.3 to 15.6 parts by mass with respect to 100 parts by mass of barium titanate as the main component, and the titanium ratio to 1 mol of barium is 0.97 to 0.98. In 2-4 to 2-6, 2-12 to 2-14, 2-19, 2-20, 2-25 and 2-29, the relative dielectric constant at 25 ° C. is 420 or more, and the relative dielectric constant at 125 ° C. 400 or more, the temperature coefficient of relative permittivity is 573 × 10 ⁻⁶ / ° C. or less in absolute value, and the curve showing the change rate of relative permittivity has two peaks in the temperature range of −55 ° C. to 125 ° C. In addition, no large hysteresis was observed in the measurement of electric field-dielectric polarization characteristics. The sample with almost no hysteresis has a polarization charge of 40 nC / cm ² or less at 0V. Dielectric ceramics obtained in Example 3 (Sample Nos. 3-2 to 3-8, 3-11 to 15- 15, 3-18 to 3-21, 3-23 to 3-27, 3-29, 3-30, 3-32 and 3-35) all have a crystal structure mainly composed of a cubic system, as in the X-ray diffraction diagram shown in FIG.

In contrast, samples outside the scope of the present invention (Sample Nos. 3-1, 3-9, 3-10, 3-16, 3-17, 3-22, 3-28, 3-31, 3- 33 and 3-34) had an absolute value of a temperature coefficient of relative permittivity larger than 1000 × 10 ⁻⁶ / ° C.

[Example 4]
Next, a sample was prepared and evaluated in the same manner as in Example 1 except that Gd ₂ O ₃ as an additive component in each composition shown in Example 1 was changed to Ho ₂ O ₃ (Sample No. 1). 4-1 to 4-35).

  Table 7 shows the preparation composition, the average particle size of the calcined powder and the firing temperature, and Table 8 shows the average particle size and characteristics of the crystal particles after firing (relative permittivity, absolute value of temperature coefficient of relative permittivity, relative permittivity The temperature change curve and the polarization charge) result are shown respectively.

Here, the addition amount of Lu ₂ O ₃ in Table 7 and the proportion of the content of Lu ₂ O ₃ in Table 8 are the same as the proportions shown in Example 1, respectively. Further, the amounts of Mg, rare earth elements (RE) and Mn shown in Table 8 are oxide equivalent amounts as in Example 1. In Table 8, “average particle diameter of crystal grains” and “absolute value of temperature coefficient of relative dielectric constant” have the same meanings as in Example 1. Further, the presence / absence of ◯ in the curve of relative permittivity temperature change and polarization charge shown in Table 8 also means the same effect as in Example 1.

As is apparent from the results in Table 8, the sample No. 4-2 to 4-8, 4-11 to 4-15, 4-18 to 4-21, 4-23 to 4-27, 4-29, 4-30, 4-32 and 4-35, 25 The relative dielectric constant at 256 ° C. was 256 or more, the relative dielectric constant at 125 ° C. was 233 or more, and the temperature coefficient of the relative dielectric constant at 25 to 125 ° C. was 980 × 10 ⁻⁶ / ° C. or less in absolute value.

In particular, with respect to 1 mol of barium, MgO is 0.017 to 0.023 mol, Ho ₂ O ₃ is HoO _3/2 , 0.0015 to 0.01 mol, MnO is 0.01 to 0.013 mol, Sample No. _{2 in which} the content of Lu ₂ O ₃ is 6.3 to 15.6 parts by mass with respect to 100 parts by mass of barium titanate as the main component, and the titanium ratio to 1 mol of barium is 0.97 to 0.98. In 4-4 to 4-6, 4-12 to 4-14, 4-19, 4-20, 4-25 and 4-29, the relative dielectric constant at 25 ° C. is 596 or more, and the relative dielectric constant at 125 ° C. 569 or more, the temperature coefficient of relative permittivity is 477 × 10 ⁻⁶ / ° C. or less in absolute value, and the curve showing the change rate of relative permittivity has two peaks in the temperature range of −55 ° C. to 125 ° C. In addition, no large hysteresis was observed in the measurement of electric field-dielectric polarization characteristics. The sample with almost no hysteresis has a polarization charge of 40 nC / cm ² or less at 0V. Dielectric ceramics obtained in Example 4 (Sample Nos. 4-2 to 4-8, 4-11 to 4-15, 4-18 to 4-21, 4-23 to 4-27, 4-29, 4-30, 4-32, and 4-35) all have a cubic crystal structure as the main component, similar to the X-ray diffraction diagram shown in FIG.

In contrast, samples outside the scope of the present invention (Sample Nos. 4-1, 4-9, 4-10, 4-16, 4-17, 4-22, 4-28, 4-31, 4- 33 and 4-34) had a temperature coefficient of relative permittivity of an absolute value larger than 1000 × 10 ⁻⁶ / ° C.

[Example 5]
Next, a sample was prepared and evaluated in the same manner as in Example 1 except that Gd ₂ O ₃ as an additive component in each composition shown in Example 1 was changed to Er ₂ O ₃ (Sample No. 1). 5-1 to 5-35).

  Table 9 shows the preparation composition, the average particle size of the calcined powder, and the firing temperature, and Table 10 shows the average particle size and characteristics of the crystal particles after firing (relative permittivity, absolute value of temperature coefficient of relative permittivity, relative permittivity The temperature change curve and the polarization charge) result are shown respectively.

Here, the addition amount of Lu ₂ O ₃ in Table 9 and the proportion of the content of Lu ₂ O ₃ in Table 10 are the same as the proportions shown in Example 1, respectively. Further, the amounts of Mg, rare earth elements (RE) and Mn shown in Table 10 are equivalent to oxides as in Example 1. In Table 10, “average particle diameter of crystal grains” and “absolute value of temperature coefficient of relative dielectric constant” have the same meanings as in Example 1. Further, the presence / absence of ◯ in the curve of the temperature change of the relative permittivity shown in Table 10 and the polarization charge column means the same effect as in Example 1.

As is clear from the results in Table 10, the sample No. 5-2 to 5-8, 5-11 to 5-15, 5-18 to 5-21, 5-23 to 5-27, 5-29, 5-30, 5-32 and 5-35, 25 The relative dielectric constant at 250 ° C. was 258 or more, the relative dielectric constant at 125 ° C. was 236 or more, and the temperature coefficient of the relative dielectric constant at 25 to 125 ° C. was 974 × 10 ⁻⁶ / ° C. or less in absolute value.

In particular, with respect to 1 mol of barium, MgO is 0.017 to 0.023 mol, Er ₂ O ₃ is ErO _3/2 and 0.0015 to 0.01 mol, MnO is 0.01 to 0.013 mol, Sample No. _{2 in which} the content of Lu ₂ O ₃ is 6.3 to 15.6 parts by mass with respect to 100 parts by mass of barium titanate as the main component, and the titanium ratio to 1 mol of barium is 0.97 to 0.98. In 5-4 to 5-6, 5-12 to 5-14, 5-19, 5-20, 5-25 and 5-29, the relative dielectric constant at 25 ° C. is 602 or more, and the relative dielectric constant at 125 ° C. 575 or more, the temperature coefficient of relative permittivity is 471 × 10 ⁻⁶ / ° C. or less in absolute value, and the curve showing the change rate of relative permittivity has two peaks in the temperature range of −55 ° C. to 125 ° C. In addition, no large hysteresis was observed in the measurement of electric field-dielectric polarization characteristics. The sample with almost no hysteresis has a polarization charge of 40 nC / cm ² or less at 0V. Dielectric ceramics obtained in Example 5 (Sample Nos. 5-2 to 5-8, 5-11 to 5-15, 5-18 to 5-21, 5-23 to 5-27, 5-29, 5-30, 5-32, and 5-35) all have a crystal structure mainly composed of a cubic system as in the X-ray diffraction diagram shown in FIG.

On the other hand, samples outside the scope of the present invention (Sample Nos. 5-1, 5-9, 5-10, 5-16, 5-17, 5-22, 5-28, 5-31, 5- 33 and 5-34) had an absolute value of a temperature coefficient of relative permittivity larger than 1000 × 10 ⁻⁶ / ° C.

Sample No. In the composition of 5-4, half of the amount of Er ₂ O ₃ was replaced with Ho ₂ O ₃ and prepared at a similar temperature to produce a dielectric ceramic. . While showing the same value as 5-4, the crystal structure was cubic. The relative dielectric constant at 25 ° C. and 125 ° C. and the absolute value of the temperature coefficient of the relative dielectric constant are shown in Sample No. It had the same characteristics as the result of 5-4, and there were two peaks in the temperature change curve of the dielectric constant, and the polarization charge was 40 nC / cm ² or less.

Sample No. For the dielectric ceramics prepared by changing Er ₂ O ₃ to Yb ₂ O ₃ in the composition of 5-4 and firing at the same temperature, the average grain size of the crystal grains is the same as that of Sample No. While showing the same value as 5-4, the crystal structure was cubic. The relative dielectric constant at 25 ° C. and 125 ° C. and the absolute value of the temperature coefficient of the relative dielectric constant are shown in Sample No. It had the same characteristics as the result of 5-4, and there were two peaks in the temperature change curve of the dielectric constant, and the polarization charge was 40 nC / cm ² or less.

It is a cross-sectional schematic diagram which shows an example of the capacitor | condenser of this invention. 2 is an X-ray diffraction diagram of a dielectric ceramic (sample No. 1-4) obtained in Example 1. FIG.

Explanation of symbols

10 Capacitor body 12 External electrode 13 Dielectric layer 14 Conductor layer

Claims (3)

A dielectric ceramic comprising crystal grains mainly composed of barium titanate and a grain boundary phase formed between the crystal grains, and magnesium is MgO with respect to 1 mol of barium constituting the barium titanate. 0.01 to 0.06 mol in terms of conversion, at least one rare earth element (RE) selected from gadolinium, terbium, dysprosium, holmium, erbium and ytterbium in an amount of 0.0007 to 0.03 in terms of REO _3/2 In addition to containing 0.0002 to 0.03 mol of manganese in terms of MnO, and further containing 3.6 to 52.1 parts by mass of lutetium in terms of Lu ₂ O ₃ with respect to 100 parts by mass of the barium titanate. And an average particle diameter of the crystal grains is 0.05 to 0.2 μm. The magnesium is 0.017 to 0.023 mol in terms of MgO and the rare earth element (RE) is 0.0015 to 0.01 mol in terms of RE ₂ O ₃ with respect to 1 mol of barium constituting the barium titanate. And 0.01 to 0.013 mol of manganese in terms of MnO, and 6.3 to 15.6 parts by mass of lutetium in terms of Lu ₂ O ₃ with respect to 100 parts by mass of barium titanate. 2. The dielectric ceramic according to claim 1, wherein a ratio of titanium to 1 mol of barium constituting the barium titanate is 0.97 to 0.98.   A capacitor comprising a laminate of a dielectric layer made of the dielectric ceramic according to claim 1 and a conductor layer.

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