JPH04331761A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic composition having high Q value and stable temperature characteristics and useful in high-frequency field such as transmitter and receiver for communication. CONSTITUTION:The objective dielectric ceramic composition has a composition of formula Bax(AyBx)Ov or Bax(ApBqCr)Ov [A is one or more elements selected from Mg, Zn, Ni, Co and Ca; B is selected from Ta and Nb; C is selected from Zr and Sn; y+z=1; p+q+r=1; 0.98<=x<=0.999] and contains 0.001-0.5wt.% of phosphorus.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition for use in the high frequency field. Dielectric ceramic compositions are widely used as dielectric resonators in high-frequency regions such as microwaves and millimeter waves, and are incorporated into filters and oscillators to improve their performance, such as reducing their size and weight and stabilizing their oscillation frequencies. It is useful for

[0002] Filters and oscillators are used as transceiver parts for communication radio waves between broadcasting satellites and ground stations, and also as transceiver parts in various communication fields using microwave and millimeter wave bands on the ground. It is also used in radar systems, etc.

Furthermore, these dielectric ceramic compositions are expected to be used as substrates for microwave circuits, taking advantage of the fact that their dielectric constant is more than twice that of alumina.

0004

2. Description of the Related Art A dielectric resonator has a small dielectric loss, in other words, a large unloaded Q (corresponding to the reciprocal of the dielectric loss), and has a predetermined dielectric constant depending on the purpose. In addition, a resonant frequency with a small absolute value of the temperature coefficient is required. In order to design such a dielectric resonator, it is desired to develop a dielectric ceramic composition suitable for various requirements.

[0005] In particular, with the recent advances in communication technology, in the field of filters, there is a need for narrower frequency band filters and filters that can handle high output, and a higher Q value is required for dielectric resonators. .

[0006] Furthermore, there is a relationship between the Q value and the resonant frequency (f).
The empirical rule that Q = C (C is a certain constant) holds true, and as the resonant frequency increases, the Q value decreases, so even when using similar equipment or elements, the operating frequency (resonant frequency from the material's perspective) As the Q becomes higher, a dielectric resonator with a higher Q value is required.

Furthermore, the temperature coefficient τf of the resonance frequency is 0.
It is required to be able to control it to an arbitrary value, mainly ppm/°C.

[0008] Also, in the field of local oscillators, 10GHz
In order to stabilize the oscillation characteristics in the above-mentioned high frequency band, it is desired to develop a dielectric resonator having a higher Q value and excellent temperature stability of the resonant frequency.

Dielectric ceramic compositions suitable for this type of resonator include Ba(Zn1/3Ta2/3)O3 system and Ba(
Compositions having a composite perovskite type structure such as Mg1/3Ta2/3)O3 system, or compositions of BaO-TiO2 system and ZrO2-SnO2-TiO2 system are known (for example, JP-A-124305-1989, 62- 874
53).

0010

[Problems to be Solved by the Invention] As mentioned above, high-frequency dielectric materials have: ■ a high dielectric constant, ■ a high Q value (low dielectric loss), and ■ a small absolute value of the temperature coefficient of the resonant frequency. Four characteristics are required: , and the value thereof can be arbitrarily controlled; and (2) small variations in each of the above characteristics are required.Recently, the requirements have become more diverse.

However, the dielectric materials conventionally used,
In particular, with regard to dielectric ceramic compositions having a composite perovskite type structure, there are almost none that satisfy all of the above four conditions, and there is a problem that one of the above characteristics (■ to ■) is lacking. was.

[0012] In particular, these dielectric ceramic compositions still have insufficient Q values, require long-time high-temperature firing during production, and require rapid temperature rise during firing. There were also many difficulties in the manufacturing process.

Based on the above, the present invention has been made by intensively researching the characteristics of various composite perovskite type dielectric ceramic compositions, and has developed a structure that has a much higher Q value than the conventional ones, excellent temperature characteristics of resonance frequency, and excellent dielectric properties. It is an object of the present invention to provide a dielectric ceramic composition which has little variation in the composition and which can be easily manufactured by a conventional manufacturing method.

[0014]

[Means for Solving the Problems] Therefore, the present invention solves the above problems by: (1) General formula: Bax(AyBz)Ow...(I)
[Here, A is at least one selected from the group consisting of Mg, Zn, Ni, Co, and Ca, B is at least one selected from Ta and Nb, and y and z are each 0. 28≦y≦0.39, 0.61≦z≦0
．． 72 (y+z=1), and w is an arbitrary number. ] For an oxide having a composition represented by
．． 98≦x≦0.999, and further 0.001 ~
A dielectric ceramic composition characterized by containing phosphorus in a range of 0.5 wt%.

(2) General formula: Bax(ApBqCr)Ow...
...(II) [Here, A is at least one member selected from the group consisting of Mg, Zn, Ni, Co, and Ca, and B
is at least one selected from Ta and Nb, and C
is at least one selected from Zr and Sn,
p, q and r are 0.26≦p≦0.34, 0, respectively
．． 53≦q≦0.70, 0.01≦r≦0.20 (however, p+q+r=1), and w is an arbitrary number. ], x is 0.98≦x
≦0.999, and further 0.001 to 0.5 w
A dielectric ceramic composition characterized in that it contains phosphorus in a range of t%. It provides:

[0016]

[Operation] In the present invention, the amount x of the barium component in the general formulas (I) and (II) is set to 0.98≦x≦0.999.
By further containing phosphorus in the range of 0.001 to 0.5 wt%, it is possible to obtain a much higher Q value than conventional dielectric ceramic compositions, and to reduce variations in dielectric properties. be able to.

That is, compared to the conventional dielectric ceramic composition in which the barium content x is 1.0 and does not contain phosphorus,
By making the amount x of the barium component slightly insufficient and also containing a trace amount of phosphorus, the Q value can be significantly improved.

[0018] Furthermore, by changing the types of elements A, B, and C in the general formulas (I) and (II) and their proportions, it is possible to control the temperature characteristics of the resonant frequency to an arbitrary value. be.

In the general formulas (I) and (II), the range of the amount x of the barium component is 0.98≦x≦0.999.
Furthermore, the phosphorus content is limited to 0.001 to 0.5
The reason for limiting the range to wt% is that if the barium amount x and phosphorus content are outside the range of the present invention, the Q value will become low or the sinterability will deteriorate. .

In particular, when the value of x is less than 0.98 or the phosphorus content is greater than 0.5 wt%, B
A second phase such as a0.5TaO3 phase is precipitated, resulting in a significant decrease in the Q value. More preferably, a dielectric ceramic composition having the highest Q value is obtained when the barium amount x is 0.995≦x≦0.997 and the phosphorus content is 0.005 to 0.04 wt%. Can be done.

Next, the invention set forth in claim 1 will be explained. The values of y and z representing the amount of each cation in the general formula (I) are particularly important in obtaining a dielectric ceramic composition with a high Q value, and each is 0.28≦y≦0.3.
9, 0.61≦z≦0.72 (y+z=1).

If these values deviate from this range, the Q value or dielectric constant will decrease. The values of y and z are preferably around 1/3 and 2/3, respectively, with this composition often achieving the highest Q values.

However, if A in the formula (I) contains 50 mol% or more of Zn, y from the above value
A composition where y is slightly larger, specifically y is 0.34 to 0.3
A high Q value can be obtained with a composition where z is around 5 and z is around 0.75 to 0.76.

A in the above formula (I) is Mg, Zn, N
At least one selected from the group consisting of i, Co and Ca
These elements can be used singly or in combination of two or more. On the other hand, B is at least one selected from Ta and Nb, and is either Ta or Nb alone or a combination of both.

[0025] However, when A contains Ca, the temperature coefficient of the resonant frequency becomes too large to be of practical use if the Ca content is increased, so the Ca content should be kept below 20 mol% of the entire A. is preferred.

Further, when Nb is included in B, there is a tendency that the dielectric constant can be increased as the proportion thereof is increased. but,
As the Nb component increases, the effect of improving the Q value of the present invention tends to become relatively small, so it is preferable to suppress the amount of Nb to 50 mol% or less based on the total B.

However, if A contains a large amount of Co, Nb
Even if B is contained in an amount of 50 mol% or more of the total B, a high effect of improving Q can be obtained.

In the invention set forth in claim 1, the highest effect in improving the Q value is obtained when B in formula (I) contains only Ta. In this case, the sinterability of the composition can also be significantly improved.

[0029] Therefore, the firing temperature can be lowered,
At the same time, variations in characteristics can be reduced. This effect is particularly effective when the ceramic composition contains elements that easily evaporate at high temperatures, such as Zn and Co.

Furthermore, compositions containing a large amount of Mg in A in formula (I) have conventionally been known as difficult-to-sinter materials, but when the present invention is applied, they can be easily sintered by normal pressureless sintering. It can be made denser.

This improvement in sinterability is thought to be due to the fact that phosphorus forms a liquid phase during firing and that barium lattice defects are introduced into the grains, which promote atomic diffusion.

In addition, factors that can particularly improve the Q value in this system include the fact that the sintered body can be easily densified, and the introduction of barium lattice defects allows divalent ions to interact with the B site in the perovskite crystal lattice. This is thought to be because regularization with Ta5+ ions occurs easily.

That is, in a system in which B in formula (I) is Ta alone, the Q value tends to improve as the atomic arrangement becomes more regularized.

In terms of Q value and temperature coefficient, the most preferred embodiment of the dielectric ceramic of the present invention is that A in the above formula (I) contains Mg as an essential component, and also contains Co or Ni, This is the case where B is Ta. Here, Co
, Ni is desirably 50% or less of the total amount of A.

Conventionally, Ba((Mg,Co)1/3Ta2
/3) O3 system, and Ba((Mg,Ni)1/3Ta
2/3) O3-based ceramic compositions had a Q value of at most 6,000 to 12,000 at 10 GHz, but in the present invention, the Q value was 30,000 at 10 GHz.
An extremely high Q value of ~35,000 or more can be obtained. Furthermore, by changing the ratio of Mg, Co, and Ni, the temperature coefficient of the resonance frequency can be reduced by several ppm around 0 ppm/°C.
It can be easily controlled within the m/°C range.

Next, the invention set forth in claim 2 will be explained. This invention further adds Zr or/and Sn to the ceramic composition of the invention described in claim 1.

A in the general formula (II) is Mg, Z
At least one element selected from the group consisting of n, Ni, Co, and Ca, and these elements may be used alone or in combination of two or more.

B is at least one selected from Ta and Nb, and is either Ta or Nb alone or a combination of both.

C is at least one selected from Zr and Sn, and is either Zr or Sn alone or a combination of both.

p, q and r representing the amount of each of these cations
are 0.26≦p≦0.34 and 0.53≦q≦, respectively.
0.70, 0.01≦r≦0.20 (however, p+q+r
=1). If these values deviate from this range, the Q value or dielectric constant will decrease.

In addition, when C in the above formula (II) is Zr alone, it is preferable that r is in the range of 0.01≦r≦0.06 in order to obtain a high Q value; In some cases, it is preferred that r be 0.10≦r≦0.20.

The dielectric ceramic composition according to the present invention according to claims 1 and 2 is usually used alone, but depending on the case, it may contain some other components, for example, several percent.
It may contain Sr, Pb, Mn, Cu, rare earth elements within a certain amount, or Fe, Al, etc. within about 1% to an extent that does not impair its characteristics.

Next, the manufacturing process will be explained. The dielectric ceramic composition according to the present invention includes carbonates of each cationic component,
Alternatively, it can be obtained by mixing and calcining starting materials such as oxides, followed by molding and firing.

Phosphorus is mixed in the form of an oxide or the like at the stage of raw material powder, or added in the form of a compound at the stage of mixed powder or calcined powder. In particular, a method in which phosphorus is added to the calcined powder in the form of an aqueous phosphoric acid solution facilitates uniform addition of phosphorus and is effective for obtaining a high-performance dielectric ceramic composition.

[0045] Furthermore, starting materials are prepared by a coprecipitation method or an alkoxide method, and the desired perovskite phase is obtained by calcining them, and then the desired dielectric ceramic composition is finally obtained. is also possible.

An example of the manufacturing process will be specifically explained. Each raw material powder is weighed to a predetermined amount and wet-mixed with a solvent such as water or alcohol. Subsequently, after removing water, alcohol, etc., it is pulverized and heated to 900-1
Calcinate in a temperature range of 300°C for about 2 to 8 hours.

[0047] It was confirmed by X-ray diffraction that this calcined powder had almost a perovskite phase. However, if the calcination temperature is low, Ba4Ta2O9 phase may be formed.

Next, a predetermined amount of phosphoric acid and an organic binder such as polyvinyl alcohol are added to this calcined powder and granulated, followed by pressure molding at a pressure of 100 to 2000 kg/cm 2 . Thereafter, this molded product was heated to 1300 to 17
The dielectric ceramic composition of the present invention can be obtained by firing at a temperature range of 00°C for about 4 to 128 hours. The firing temperature depends on the type and amount of the component elements of the composition, the phosphorus content, the particle size and shape of the raw material powder, etc., but is between 1450 and 1600°C.
It is common to fire at a certain level.

For example, when A in formula (I) contains a large amount of Mg and B contains a large amount of Ta, it is preferable to sinter at a relatively high temperature of around 1600°C. On the other hand, A contains Zn, Co
or if B contains a large amount of Nb, 1
It may be fired at a relatively low temperature of about 450 to 1550°C.

The obtained dielectric ceramic composition becomes a dielectric resonator as it is or by processing it into an appropriate shape and size as required.

Finally, although the dielectric ceramic composition of the present invention is mainly used as a dielectric resonator, it can also be used as a microwave IC substrate and as a material for dielectric adjustment rods and the like.

Furthermore, taking advantage of the small dielectric loss,
It is a material that can be applied to various fields such as window materials for high-frequency plasma furnaces.

[0053]

[Examples] The present invention will be explained in detail below with reference to Examples.

[0054]

[Example 1] As one of the representative embodiments of the present invention,
Examples in which A in the general formula (I) is Mg or Co, and B is Ta will be described in detail.

[0055] High purity BaCO3 and CoO are used as raw materials.
, MgO 2 , and Ta2O5, each raw material powder was weighed so that the molar composition ratio of each component became the composition shown in sample numbers 1 to 40 in Table 1 after sintering. These were wet mixed in a ball mill for 24 hours using ethanol as a medium.

[0056] Thereafter, it was dried using an evaporator and calcined in the air at about 1150 to 1250°C for 4 hours. At this time, the optimal conditions for calcination time and temperature differ slightly depending on the amount, particle size distribution, and composition of the mixed powder, but X-ray diffraction analysis shows that almost a single perovskite phase is formed in all cases. confirmed.

Next, an aqueous phosphoric acid solution was added to this calcined powder so that the phosphorus content was 0.001 to 0.5 wt%, and polyvinyl alcohol was further added as a binder to perform granulation. .

[0058] The granulated powder was pressure-molded into a cylindrical shape at a pressure of 1000 kg/cm2. And this molded product is 1450~1
A dielectric ceramic composition of the present invention was obtained by firing at 600°C for 16 to 64 hours.

For evaluation of the dielectric, the thus obtained ceramic composition was processed into a cylinder shape with a diameter of about 10 mmφ and a height of about 5 mm, and the dielectric cylindrical resonator method was used to process the ceramic composition into a cylinder with a frequency of 9.5 to 10.5 GHz.
The Q value and dielectric constant were measured. Further, each sample was placed in a constant temperature bath and the temperature coefficient (τf) of the resonance frequency at 25 to 55°C was measured.

Table 1 summarizes the characteristics of the dielectric resonator manufactured by the above method. Note that samples marked with * are outside the scope of this invention, and all others are within the scope of this invention.

[0061] Furthermore, the Q value is a value converted to 10 GHz based on the empirical rule that f·Q=constant (f: resonant frequency). As shown in the table, the barium amount x is 0.98≦x≦0.9
99 and further added 0.001 to 0.5 wt phosphorus.
%, it was possible to obtain a dense dielectric resonator with a high Q value and a relative density of 95% or more.

In particular, the barium amount x is set to 0.995≦x≦0
．． 997, phosphorus content from 0.005 to 0.1 wt
%, it was possible to obtain a very high Q value of approximately 30,000 or more at 10 GHz. Moreover, τf of the dielectric resonator could be arbitrarily controlled by changing the ratio of Mg and Co.

[0063]

[Example 2] High purity BaCO3 and MgO as raw materials
, ZnO , NiO , CoO , CaCO3 , M
Required powders were selected and prepared from gO, Ta2O5, Nb2O5, and after sintering, each raw material powder was weighed and blended so that the molar composition ratio of each component became the composition shown in sample numbers 41 to 106 in Table 2.

The obtained raw material mixture was treated in the same manner as in Example 1 to produce a dielectric ceramic composition, and its dielectric properties were measured. The results are summarized in Table 2. Note that samples marked with * are outside the scope of this invention, and all others are within the scope of this invention.

[0065] Furthermore, the Q value is a value converted to 10 GHz based on the empirical rule that f·Q=constant (f: resonant frequency).

[0066]

[Example 3] High purity BaCO3 and MgO as raw materials
, ZnO , NiO , CoO , CaCO3 , M
gO, Ta2O5, Nb2O5, ZrO2, Sn
Required powders were selected and prepared from O2, and after sintering, each raw material powder was weighed and blended so that the molar composition ratio of each component became the composition shown in sample numbers 107 to 157 in Table 3.

The obtained raw material mixture was treated in the same manner as in Example 1 to produce a dielectric ceramic composition, and its dielectric properties were measured. The results are summarized in Table 3. Note that samples marked with * are outside the scope of this invention, and all others are within the scope of this invention.

Furthermore, the Q value is a value converted to 10 GHz based on the empirical rule that f·Q=constant (f: resonant frequency).

[0069]

[Table 1]

[0070]

[0071]

[Table 2]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[Table 3]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

Effects of the Invention As described above, the present invention provides an excellent dielectric ceramic composition that has a large dielectric constant, a high no-load Q, and can arbitrarily control the temperature characteristics of the resonant frequency in a high frequency region. This made it possible. In particular, depending on the composition, 30,000 to 35,000 at 10GHz
Since a very high Q value such as the above can be obtained, it is also possible to use it in a higher frequency range.

Claims (2)

[Claims] [Claim 1] General formula: Bax(AyBz)Ow [
Here, A is at least one selected from the group consisting of Mg, Zn, Ni, Co, and Ca, and B is Ta and N.
at least one selected from b, where y and z are
0.28≦y≦0.39, 0.61≦z≦0, respectively.
72 (y+z=1), and w is an arbitrary number. ], x is 0.
98≦x≦0.999, and further 0.001 to 0
．． A dielectric ceramic composition characterized by containing phosphorus in a range of 5 wt%. [Claim 2] General formula: Bax(ApBqCr)Ow
[Here, A is at least one selected from the group consisting of Mg, Zn, Ni, Co and Ca, B is at least one selected from Ta and Nb, and C is at least one selected from Zr and Sn. 1 type, p, q and r are 0.26≦p≦0.34 and 0.53≦, respectively.
q≦0.70, 0.01≦r≦0.20 (however, p+q
+r=1), and w is an arbitrary number. ], x is 0.98≦x≦0.9
99 and further contains phosphorus in a range of 0.001 to 0.5 wt%.