JPH06333428A - Dielectric composition - Google Patents

Abstract

PURPOSE:To obtain a dielectric composition to be used in an electronic part field and a semi-conductor device field mainly and having the structure phase change corresponding to the temperature change and the pressure change or the like. CONSTITUTION:This dielectric composition has the compound perovskite crystal structure expressed with A(BI1/3BII2/3)O3, and the mean ion radius (R) of the A site thereof exists in a range of 1.06<=R<=1.37, and the structure phase change is generated at a temperature between the liquid nitrogen temperature and 400 deg.C. Though the change of the dielectric factor with the structure phase change is very small, since the change thereof shows maximum and slope, the zero temperature coefficient is obtained by controlling the radius of ion. Especially the perovskite compound, of which dielectric factor can be changed freely with temperature change, is obtained by combining new A site ions composed of Ba, Sr and Cr.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is a material that undergoes a structural phase transition due to temperature change, pressure change, etc., and by utilizing the physical property change caused by this phase transition, it can be applied to the electronic industry field and various sensor business fields. It is applied. For example, the non-linear temperature change of the dielectric constant due to the structural phase transition is caused by the thin film dielectric capacitor and the insulating film which are being used in the field of electronic parts typified by capacitors and dielectric resonators and semiconductor integration technology. Has a high utility value in the field of

[0002]

2. Description of the Related Art In the field of electronic parts and semiconductor devices, the development of materials and parts with better temperature stability of characteristics is progressing with technological development toward higher frequency, energy saving and faster response in recent years. Is required.

As a capacitor material for temperature compensation, which is one of electronic components required to have high temperature stability, a paraelectric material having a small change in permittivity with temperature in an operating temperature range (for example, 20 to 85 ° C.). Is used. As a typical material, the dielectric constant is 75 to 80 and the temperature coefficient of the dielectric constant (τ
ε) Titanium oxide with -800 ppm / ° C, dielectric constant 140 ~
CaO with τε of -1200 to -1800ppm / ° C at 150
・ NTiO ₂ (n = 1 to 2), and a dielectric constant of 200 to
SrO of 260 with τε of -3200 to -3400ppm / ° C
There are nTiO ₂ (n = 1 to 1.5) and the like. A characteristic of these materials is that the dielectric constant decreases monotonically with increasing temperature. Therefore, when it is desired to further reduce the temperature coefficient to almost zero, the dielectric constant is as small as 12 to 18, but τε
Has a positive value of 140 to 190 ppm / ° C., and the dielectric constant monotonically increases with increasing temperature nMgO · TiO ₂ (n =
1 to 4) and the like are appropriately combined with the above-mentioned materials, and more accurate ones are required to meet severe recent needs.

On the other hand, as a technical field in which the temperature change control of the dielectric constant with higher accuracy than that of the capacitor is required, there is a technology relating to a dielectric resonator used as a frequency filter in the field of wireless communication. When using this dielectric resonator as a filter, considering the compatibility with the temperature coefficient of other parts and the case in the operating temperature range of 20 to 85 ° C., finally, as a unit, in the operating temperature range of the resonance frequency, The change is required to be near zero. Since the temperature coefficient τf of the resonance frequency satisfies a function of τf = −α−τε / 2 between the linear expansion coefficient α of the material and the temperature coefficient τε of the dielectric constant, empirically, α and τε are We have developed materials with appropriate values to realize materials with as low a temperature coefficient of resonance frequency as possible. In this field, it is desired to develop a material whose temperature coefficient can be freely controlled, including its application to an oscillator.

[0005]

SUMMARY OF THE INVENTION The present invention addresses the above technical problems in the fields of electronic components and semiconductor devices,
It is an object of the present invention to provide a dielectric composition that can significantly reduce the change in dielectric constant with temperature and can change its nonlinearity and gradient from positive to negative freely.

[0006]

In order to achieve the above object, the present invention has the following structures. That is,
(1) A compound perovskite compound having a crystal structure represented by the structural formula A (BI _1/3 BII _2/3 ) O _{3, in} which the BI site is a divalent ion and the BII site is a pentavalent ion, and is a liquid. A structural phase transition occurs between nitrogen temperature and 400 ° C,
The average ionic radius (R) of the site is 1.06 ≦ R ≦ 1.
A dielectric composition characterized in that in the range of 37, (2) perovskite type compound in the preceding paragraph, wherein the formula _{(Ba x Sr y Ca z)} (BI 1/3 BII 2/3) O 3 And 0 ≦ x ≦ 0.7, 0.4 ≦ y ≦ 1.0, 0 ≦ z ≦
It is a dielectric composition having a composition range represented by 0.5.

The present invention will be described in detail below. The basis of the present invention is that, when the A site of a material having a complex perovskite crystal structure is substituted to form a solid solution, a material having an average ionic radius of the A site within a certain range has not been heretofore known. It is a discovery that there is a structural phase transition. This structural phase transition is due to splitting of high-angle peaks in X-ray diffraction, appearance of new superlattice reflection in electron diffraction,
It is characterized by the splitting of peaks in the Raman spectrum. And, for example, focusing on the temperature change of the dielectric constant,
It has a non-linear maximum or changes in gradient. If a material capable of intentionally controlling such physical property changes is developed, various epoch-making effects such as a zero temperature coefficient and a switching effect can be realized.

First, in comparison with the conventionally known structural phase transition, for example, in the structural phase transition between a ferroelectric phase represented by BaTiO ₃ and a paraelectric phase, the dielectric constant changes by two to three digits. As a result, a small change in the temperature change cannot be expected. On the other hand, the conventionally known SrT
The phase transition temperature of the paraelectric phase typified by i0 ₃ was not near room temperature and was either too high or too low for practical use. On the other hand, if the structural phase transition of a material having a complex perovskite crystal structure can be controlled in the range of liquid nitrogen temperature to 400 ° C. around room temperature, high temperature stability and controllability are required. We thought that it would have a very high application value in various applications.

As a result of earnest research based on this idea, it was found that the temperature change of the dielectric constant can be controlled around room temperature by controlling the ionic radius of the A site, and the present invention was completed. . In the present invention, attention was paid to the ionic radius of the A site rather than the B site. In order to control the properties of the composite perovskite type compound, it is a conventional means to utilize the substitution effect of the A site and the B site, but it is not such an idea, but BO ₆ oxygen centered on the B site ion is used. By forming a crystal skeleton structure between the octahedron and the A site ion and controlling the balance of this skeleton structure, the physical properties of the complex perovskite compound were changed to obtain the desired material. Therefore, it is possible to provide a composition characterized by the average value of the ionic radius of the A site without giving a large restriction to the B site ion in the approximate center of gravity of the oxygen octahedron.

As described above, in order to keep the structural phase transition temperature between the liquid nitrogen temperature and about 400 ° C., it is necessary to properly select the average ionic radius entering the A site of the composite perovskite type crystal structure. . To calculate the average ionic radius, use F. S. The values of Goldschmit's ionic radii shown in Table 1.1b of "Illustrated Fine Ceramics Crystal Chemistry" by Galassau (Agne Technical Center) are used. In this table, the ionic radius of Ba ⁺² ions is 1.
43, Ca ⁺² is 1.06, K ⁺ is 1.33, La ⁺³ is 1.22, Pb ⁺² is 1.32, and Sr ⁺² is 1.27. A value obtained by weighting and averaging the values of the ion radius of each of these ions with the addition ratio of each ion is the average ion radius of the A site ion. When the average ionic radius (R) thus obtained is smaller than 1.06, the permittivity monotonically increases with temperature change, and conversely, when it is larger than 1.37, the permittivity monotonically decreases. Therefore, in order to control the gradient of this temperature change to be positive or negative, 1.06 ≦ R ≦ 1.3
We found that a range of 7 was good. Most of the composite perovskite type oxides that have been conventionally used as dielectric ceramic compositions have an average ionic radius of 1.39 ≦ R ≦.
The range is 1.43, which is clearly different from the material to be provided by the present invention.

Specifically, in the composition range that satisfies the range of the average ionic radius due to the combination of ions, the A site is B
When it is composed of a and Sr, the ratio of Ba: Sr is 0.62.
The range is 5: 0.375 to 0: 1. A site is B
When composed of three kinds of ions, a, Sr, and Ca, the composition range is represented by a composition triangle in which the three vertices correspond to Ba, Sr, and Ca occupying 100% of the A sites. In the composition range satisfying the condition of the average ionic radius, the ratio of (Ba: Sr: Ca) in the composition triangle is (0.
84: 0: 0.16), (0.625: 0.375:
0), (0: 0: 1), and (0: 1: 0) correspond to the sides of a quadrangle formed by connecting four points and the enclosed area. When the A site is composed of three kinds of ions of Ba, Sr and Pb, the desirable composition range satisfying the condition of the average ionic radius is that the ratio of (Ba: Sr: Pb) in the composition triangle is
(0.455: 0: 0.545), (0.625: 0.
375: 0), (0: 0: 1), and (0: 1: 0), which correspond to the sides and the enclosed area of a quadrangle formed by connecting four points. When the A site is composed of four kinds of ions of Ba, Sr, K and La and the molar ratios of K and La are always the same, the desirable composition range satisfying the condition of the average ionic radius is Ba: Sr: K _0.5 La
The ratio of _0.5 ) is (0.613: 0: 0.387),
(0.625: 0.375: 0), (0: 0: 1),
It corresponds to a side of a quadrangle formed by connecting four points of (0: 1: 0) and an enclosed area.

As described above, the ranges satisfying the condition of the average ionic radius have been concretely shown for some of the material systems containing 3 to 4 kinds of ions at the A site, but the materials provided by the present invention have been shown so far. The combination is not limited to the combination of ions, and for example, Nd, Sm, Ra, Ce, Mg, L
It is also possible to select from i and Eu. Furthermore, as a result of studying the combination of A site ion species, especially Ba, S
It has been found that the combination of r and Ca has good controllability of the dielectric constant. At this time, Ba, Sr, C occupying the A site
It is desirable that the a ions completely dissolve in each other,
For that purpose, 0 ≦ x ≦ 0.7, 0.4 ≦ y ≦ 1.0,
It is desirable that the composition range is represented by 0 ≦ z ≦ 0.5. If it deviates from this composition range, the elements that cannot be completely dissolved become the main components and lead to the formation of the second phase.

On the other hand, in the present invention, even if there is a heterogeneous phase, if the perovskite type compound phase as the main component occupies the majority, there is no problem in controlling the dielectric properties. That is, in the present invention, the subject is to cause the structural phase transition temperature of the composite perovskite type compound in the disclosed temperature range, depending on the purpose, a complex containing such a composite perovskite type compound, for example, There is no problem even if it is applied as a composite with another ceramic material or an organic material such as a polymer. Ions entering the B site of the complex perovskite type crystal structure are not particularly limited, but at the same time as the phase transition occurs at a desired temperature, the charge neutral condition of the material is satisfied, and the regularity of the ionic arrangement of the B site is maintained. It is necessary to adjust the number and proportion of ions to be generated. Ions that enter the B site and obtain a dielectric material having excellent characteristics include Mg, Zn, Ni, Co, Cr, Mn, Cu, and F.
e, Ta, Nb, W and the like.

Next, the manufacturing method will be briefly described, and the application method thereof will be described. BaCO as a raw material
₃ , SrCO ₃ , CaCO ₃ , MgO, Ta ₂ O _5, etc. are mixed in a composition range that finally causes a structural phase transition, and calcined in a temperature range of about 1000 to 1300 ° C. to obtain a composite perovskite. After obtaining the mold compound, a shape suitable for the purpose is imparted by molding or the like, and the material is obtained by firing in the temperature range of about 1400 ° C to 1700 ° C. Since it is porcelain after sintering, it can be formed into any shape by machining. Further, the composite perovskite type compound powder can be applied to various fields without being sintered.

Further, instead of using powder as a starting material, a thin film made of the composite perovskite type compound of the present invention can be produced by a thin film manufacturing technique represented by a CVD method, a PVD method or the like. Due to advances in semiconductor technology,
The integration of devices having various functions is a major technology flow in the future, and materials such as the present invention having a structural phase transition and having excellent temperature stability are often used in combination with various circuit devices. A wide range of applications are possible as functional elements and thin film capacitors.

[0016]

According to the present invention, it is possible to obtain a new dielectric material whose dielectric constant can be freely changed with temperature. In addition, the material provided by the present invention can change not only the dielectric property depending on temperature but also the voltage property and the oxygen partial pressure in the atmosphere to change the dielectric property. It can also be used for.

[0017]

【Example】

(Example 1) High-purity BaCO ₃ and SrCO as raw materials
₃ , CaCO ₃ , K ₂ CO ₃ , La ₂ O ₃ , MgO, T
using a ₂ O _5, wherein _{{Ba x Sr y Ca z (} K 0.5 La 0.5) w} (Mg 1/3
When written as Ta _2/3 ) O ₃ , the average ionic radius R of A site is 1.06
Weighed so as to be in the range of ≤R≤1.37, and wet-mixed for 16 hours with a ball mill using ethanol as a medium.
This was dried using a rotary evaporator and calcined in the air at 1200 ° C. for 4 hours. Next, the pulverized calcined powder was pressure-molded into a cylindrical shape with a pressure of 2000 kgf / cm ² . This molded body was fired at 1400 to 1600 ° C. for 4 to 16 hours to obtain a sintered body. This sintered body was processed to have a diameter of 9 mm and a height of 4.5 mm. The phase transition temperature of the thus obtained dielectric was measured using Raman spectroscopy or the like.
The results are shown in Table 1. Sample Nos. 1-5 are within the scope of the invention and the samples showed a phase transition. Sample No. 6 was outside the scope of the present invention, and no phase transition could be confirmed.

[0018]

[Table 1]

(Example 2) High purity BaCO as a raw material
_{3, SrCO 3, CaCO 3,} MgO when using a Ta ₂ O _5, wrote formula _{(Ba x Sr y Ca z)} (Mg 1/3 Ta 2/3) O 3, x = 0.41, y = 0.54, z = 0.0
It was weighed so as to be 5, and wet-mixed for 16 hours with a ball mill using ethanol as a medium. This was dried using a rotary evaporator and then dried in the air at 1200 ° C for 4
The time was calcined. Next, the pulverized calcined powder is 2000
It was pressure-molded into a cylindrical shape with a pressure of kgf / cm ² . This molded body was fired at 1600 ° C. for 16 hours to obtain a sintered body. This sintered body was processed to have a diameter of 16 mm and a height of 0.7 mm.
Gold electrodes were attached to both end faces of the thus obtained dielectric, and the temperature dependence of the dielectric constant was measured. An impedance analyzer was used for the measurement. The result is shown in FIG. The vertical axis of FIG. 1 represents the formula Δε (T) / ε (25) = {ε (T) −ε.
(25)} / ε (25), which is the change in the dielectric constant at each temperature, normalized by the dielectric constant at 25 ° C.
The temperature change of the dielectric constant is flat at 20 to 85 ° C., and the temperature coefficient thereof is 0.3 ppm / ° C.

[0020]

As described above, according to the present invention, the dielectric constant has a significantly small temperature change, and the dielectric constant and gradient of which can be freely changed from positive to negative. The body composition can be obtained, which is extremely useful for business fields such as electronic parts and semiconductor devices.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a phase transition temperature and a change in dielectric constant temperature according to the present invention.

Claims (2)

[Claims] 1. A crystal structure represented by structural formula A (BI _1/3 BII _2/3 ) O ₃ , wherein the BI site is a divalent ion, BII
A complex perovskite type compound whose site is a pentavalent ion, and the average ionic radius (R) of the A site which causes a structural phase transition between liquid nitrogen temperature and 400 ° C. is 1.06 ≦
A dielectric composition having a range of R ≦ 1.37. 2. The perovskite compound according to the above item,
Chemical formula _{(Ba x Sr y Ca z)} (BI 1/3 BII 2/3) O
₃ and 0 ≦ x ≦ 0.7, 0.4 ≦ y ≦ 1.0, 0 ≦
The dielectric composition according to claim 1, wherein the dielectric composition has a composition range represented by z ≦ 0.5.