JP2005194114A - Dielectric porcelain composition for electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric porcelain composition for electronic devices which has a high Qf<SB>0</SB>value in the vicinity of a relative dielectric constant εr of 39 and has such dielectric characteristics that the temperature coefficient τf of resonance frequency is small and has a value controllable in the positive and negative directions in a wide range. <P>SOLUTION: In a La-Pr-Al-Ga-Sr-Ti oxide dielectric porcelain, the content of each element is squeezed into a specified range and a part of Sr is substituted by Ca. Thereby, a dielectric porcelain composition of which the main phase is a (1-x)(La<SB>1-y</SB>Ln<SB>y</SB>)(Al<SB>1-z</SB>Ga<SB>z</SB>)O<SB>3</SB>-x(Sr<SB>1-m</SB>Ca<SB>m</SB>)TiO<SB>3</SB>solid solution and in which an Al-Ga-Sr oxide solid solution and/or an Al-Ga oxide solid solution and an Sr oxide have precipitated at the grain boundary, is yielded, achieving the purpose. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dielectric porcelain composition having optimum characteristics for microwave / millimeter wave electronic devices used in dielectric resonators, dielectric filters, phase shifters, etc., and Al-Ga-Sr system at grain boundaries. The present invention relates to a novel dielectric ceramic composition for electronic devices in which a solid solution of an oxide and / or a solid solution of an Al-Ga oxide and an Sr oxide are present.

Dielectric ceramic compositions are widely used in electronic devices intended for high frequency regions such as microwaves and millimeter waves. The characteristics required for these applications are as follows: (1) In the dielectric, the wavelength is shortened to 1 / εr ^1/2 , so the relative permittivity εr is large for the demand for miniaturization, (2) The dielectric loss at high frequency is small, that is, the Qf value is high, and (3) the temperature coefficient τf of the resonance frequency is small and stable. It is also important that the temperature coefficient τf can be controlled within a predetermined range.

Conventionally, as such a high-frequency dielectric ceramic composition, for example, La-Ti-Al-O system (Non-Patent Document 1) is known, the characteristics are εr = 36, Qf ₀ value = 45,000 GHz, τf = -2 ppm / ° C, and Qf ₀ value is low.
Japan, J.appl, phys, Vol.36 (1997) 6814

In addition, in the Ba (Zn _1/3 Nb _2/3 ) O ₃ system (non-patent document 2), εr = 41, Qf ₀ value = 86,000 GHz, τf = + 31 ppm / ° C., A dielectric ceramic composition having a small τf has not been obtained.
Electronic Ceramics September 1993, page 3

In recent years, Ln-Al-Ca-Ti-based oxide dielectric ceramics (Patent Document 1), La-Al-Sr-Ti-based oxide dielectric ceramics (Patent Document 2) as materials having a high dielectric constant and Qf value Has been proposed. Although these materials have excellent characteristics such as a relative dielectric constant εr of 30 to 48 and a Qf ₀ value of 20,000 to 75,000 (value at 1 GHz), a dielectric ceramic composition having a small τf has not been obtained. .
Japanese Patent No. 2625074 Japanese Patent Laid-Open No. 11-130528

In addition, in the Ln-Al-Ca-Sr-Ba-Ti-based oxide dielectric ceramic, it has been proposed to improve the Qf value by including α-Al ₂ O ₃ as a crystal phase (Patent Document 3). ). This material has excellent characteristics such as a Qf value of 30,000 or more, but τf is a relatively large value, positive or negative.
Japanese Patent Laid-Open No. 11-106255

  Although these materials have improved relative permittivity εr and Qf values, the characteristics of τf are not sufficient, and the idea of controlling τf is not made.

The applicant previously proposed a dielectric ceramic composition for microwaves having dielectric properties of εr = 35 to 45, Qf ₀ value = 50,000 GHz or more, and τf = 0 ± 10 ppm / ° C. (Patent Document 4). This composition improves the Qf ₀ value by adding a specific amount of Ga in the La-Al-Sr-Ti-based oxide, and further increases the τf value by adding a specific amount of Pr to 0 ± 10 ppm. / ° C.
WO 02/36519 A1 Gazette

  According to the above-mentioned proposal by the applicant of the present application, it is possible to substantially satisfy the characteristics (1) to (3) required for the dielectric ceramic composition described above, but the temperature coefficient τf is controlled within a predetermined range. In particular, there is a problem that control in the positive direction is not possible.

This invention has a high Qf ₀ value when the relative dielectric constant εr is in the vicinity of 39, the temperature coefficient τf of the resonance frequency is small, and has a dielectric characteristic capable of controlling the value in a wide range in the positive and negative directions. The object is to provide a dielectric ceramic composition for electronic devices.

The inventors have aimed for a dielectric ceramic composition having a structure in which the temperature coefficient τf of the resonance frequency is small and its value can be controlled in a wide range in the positive and negative directions in La-Al-Sr-Ti-based oxides. In addition, as a result of intensive studies, in the La-Pr-Al-Ga-Sr-Ti-based oxide dielectric porcelain, the content of each element is narrowed down to a specific range, and a part of Sr is replaced by Ca. , Al-Ga- in _{(1-x) (La 1} -y Ln y) (Al 1-z Ga z) a _{O 3 -x (Sr 1-m} Ca m) TiO 3 solid solution as a main phase, the grain boundary Sr-based oxide solid solution and / or Al-Ga-based oxide solid solution and Sr oxide precipitated structure, relative permittivity εr near 39,
Qf ₀ value has a high characteristic of 57,000 or more, and the temperature coefficient τf of the resonance frequency,
The present invention was completed by discovering that it can be controlled in the range of -8 ppm / ° C to 6 ppm / ° C.

That is, the present invention is, (1-x) (La 1-y Ln y) (Al 1-z Ga z) O 3 -x (Sr 1-m Ca m) TiO 3 solid solution (where, Ln is Pr, Nd At least one of x, y, z, and m satisfy the following values), and a solid solution of an Al-Ga-Sr oxide or a solid solution of an Al-Ga oxide and an Sr oxide at the grain boundary. Or a dielectric ceramic composition for an electronic device, characterized by the presence of a solid solution of Al-Ga-Sr-based oxide and a solid solution of Al-Ga-based oxide and Sr oxide.
0.5 ≦ x ≦ 0.6, 0 <y ≦ 0.2, 0 <z ≦ 0.05, 0 <m ≦ 0.3

The present invention also provides the dielectric ceramic composition for an electronic device, characterized in that α-Al ₂ O ₃ does not substantially exist at the grain boundary in the above configuration.

According to the present invention, as a dielectric ceramic for an electronic device, the relative dielectric constant εr is in the vicinity of 39, the Qf ₀ value is 57,000 or more, and the temperature coefficient τf of the resonance frequency is in the range of −8 ppm / ° C. to 6 ppm / ° C. Can be controlled.

  According to the present invention, in the La-Ln-Al-Ga-Sr-Ti-based oxide dielectric ceramic, the temperature coefficient τf can be controlled by replacing part of Sr with Ca, and calcining is performed. The reactivity at the time is improved, and calcination can be performed at a temperature of 1200 ° C. to 1300 ° C., which has been difficult with conventional La—Al—Sr—Ti oxide dielectric ceramics.

The dielectric ceramic composition according to the invention, (1-x) (La 1-y Ln y) (Al 1-z Ga z) a _{O 3 -x (Sr 1-m} Ca m) TiO 3 solid solution as a main phase In addition, a specific oxide solid solution, that is, a solid solution of an Al—Ga—Sr-based oxide and / or a solid solution of an Al—Ga-based oxide and an Sr oxide exist in the grain boundary.

In the present invention, (1-x) (La 1-y Ln y) (Al 1-z Ga z) O 3 -x (Sr 1-m Ca m) components of TiO ₃ solid solution, Ln, x, y, z The reasons for limiting m are as follows. Ln is at least one or two of Pr and Nd. Ln can move τf in the positive direction by using Pr, and τf can be moved in the negative direction by using Nd.

x is indicated by _{(La 1-y Ln y)} (Al 1-z Ga z) a component range of O ₃ (1-x), the component range of _{(Sr 1-m Ca m)} TiO 3 (x) 0.5 ≦ x ≦ 0.6 is a preferable range. When x is less than 0.5, the relative dielectric constant εr decreases, and when it exceeds 0.6, the relative dielectric constant εr increases, and the Qf ₀ value decreases to less than 57,000.

y represents the component range of La and Ln, and 0 <y ≦ 0.2 is a preferable range. If y exceeds 0.2, the Qf ₀ value decreases and τf increases, which is not preferable.

z represents the component range of Al and Ga, and 0 <z ≦ 0.05 is a preferable range. If z exceeds 0.05, the Qf ₀ value decreases, which is not preferable. In particular, Ga in the present invention is a very important element, and the presence of Ga makes it possible to obtain the above Ln substitution effect and the following Ca substitution effect. That is, even if a part of Sr is added to Ca in a component system in which Ga does not exist, the Qf ₀ value is low and τf cannot be controlled.

  m represents a component range of Sr and Ca, and 0 <m ≦ 0.3 is a preferable range. If m exceeds 0.3, τf becomes too large. By replacing part of Sr with Ca, the temperature coefficient τf can be controlled and the reactivity during calcination can be improved. Conventionally, La-Al-Sr-Ti oxide dielectrics It is possible to calcine at a temperature of 1200 ° C to 1300 ° C, which was difficult with porcelain.

In the present invention, by the respective elements to limit the component range of the, (1-x) (La 1-y Ln y) (Al 1-z Ga z) O 3 -x (Sr 1-m Ca m ) TiO ₃ solid solution as the main phase, at its grain boundary,
(1) Al-Ga-Sr oxide solid solution,
(2) Al-Ga oxide solid solution and Sr oxide,
(3) Al-Ga-Sr oxide solid solution and Al-Ga oxide solid solution and Sr oxide,
Either of which is deposited and present.

  The presence of the grain boundary can be confirmed by EPMA analysis of the sintered body of the dielectric ceramic composition. However, although it can be confirmed that all of the Sr oxide is not contained in the main phase, whether it exists as a solid solution of the Al-Ga-Sr oxide at the grain boundary or the solid solution of the Al-Ga oxide. Since it is difficult to distinguish whether it exists as Sr oxide, the above (1) to (3) are limited.

In the dielectric ceramic composition of the present invention, it is clear that at least Al forms a solid solution of Ga and oxide and exists at the grain boundary, as will be demonstrated by the examples described later. Therefore, Al is not present as α-Al ₂ O ₃ in the present porcelain composition, and α-Al ₂ O ₃ is substantially absent from the constitution.

  The method for producing a dielectric ceramic composition according to the present invention includes mixing of raw material powder, wet or dry mixing, drying, calcining, wet or dry grinding, drying, granulation, molding, sintering, and each device as appropriate. It can manufacture easily by obtaining the sintered compact by the well-known method to select.

Example 1
As starting materials, high-purity powders of La ₂ O ₃ , Nd ₂ O ₃ , Pr ₆ O ₁₁ , Al ₂ O ₃ , Ga ₂ O ₃ , SrCO ₃ , CaCO ₃ , and TiO ₂ were prepared. Each powder was blended as shown in Table 1, mixed in pure water and dried to obtain a mixed powder having an average particle size of 0.7 to 1.4 μm.

  Next, the mixed powder was calcined at 1100 ° C. to 1300 ° C. for 2 to 6 hours depending on the composition. The obtained calcined powder was pulverized to 0.6 to 1.5 μm by wet pulverization, and then the pulverized powder was dried. Further, PVA was added to the dried powder, mixed, and granulated by a granulator.

The obtained granulated powder was molded to a molding density of 2 to 4 g / cm ³ with a uniaxial press machine. The obtained molded body was debindered at 300 ° C. to 700 ° C. and then sintered at 1500 ° C. to 1800 ° C. for 10 to 50 hours in an atmosphere having an oxygen concentration of 50 to 100% to obtain a sintered body.

  The obtained sintered body was processed into φ10 mm × 4 to 9 mm to obtain a test piece. The obtained test piece was measured for relative permittivity, Qf value, and τf value by H & C method using a network analyzer. Table 1 shows the measurement results.

  Test pieces Nos. 1 to 43 are examples according to the present invention, and Nos. 44 to 56 are comparative examples. No. 44 is the same as in Example No. 1, and when y (Ln), z (Ga), m (Ca) is not included, No. 45-49 is z in Example No. 1-5 composition. When (Ga) is not included, No. 50 is when Example No. 1 composition does not contain m (Ca), No. 51 and 52 are when Example No. 1 composition is x out of range, No. .53 does not include y (Ln) in the composition of Example No. 1, when x is out of range, No. 54 does not contain y (Ln) in the composition of Example No. 1, .55 is a comparative example showing a case where z (Ga) is out of range in the composition of Example No. 1, and No. 55 is a comparative example showing a case where m (Ca) is out of range in the composition of Example No. 1.

  As apparent from Table 1, the test piece according to the present invention had a Qf value in the vicinity of a relative dielectric constant of 39, 57,000 to 88,000, and a τf value in the range of -8 ppm / ° C. to 6 ppm / ° C. It is apparent that τf can be controlled within the above range by selecting.

Example 2
The results of EPMA analysis of test piece No. 1 in Example 1 are shown in FIG. 1, and schematic diagrams thereof are shown in FIGS. The upper left of Fig. 1 is BEI (composition image, schematic diagram is shown in Fig. 2), the upper middle is the characteristic X-ray image of Al (schematic diagram is shown in Fig. 3), the upper right is the characteristic X-ray image of Ga (Fig. 4). The middle left is a characteristic X-ray image of Ti (schematic diagram is shown in FIG. 5), the middle middle is a characteristic X-ray image of La (schematic diagram in FIG. 6), the middle right is Sr Characteristic X-ray image, lower left is a characteristic X-ray image of Ca.

  In the composition image on the left in the upper part of FIG. 1, the part that appears white (the part surrounded by a thin black line in the entire ground part of the schematic diagram in FIG. 2) is the main phase, and the gray part (the black line and thick line in the schematic diagram). The part surrounded by the black line) is the grain boundary. In the characteristic X-ray images of Al and Ga, the same part as the grain boundary part in the composition image (in the schematic frame in FIGS. 3 and 4) is white. This indicates that Al and Ga exist at the grain boundaries. On the contrary, in the characteristic X-ray images of Ti and La, the same part as the grain boundary part in the composition image (within the line frame in the schematic diagrams of FIGS. 5 and 6) is black. This indicates that Ti and La are not present at the grain boundaries.

  As for Sr oxide, the chemical form existing at the grain boundary is not clear in the characteristic X-ray image by EPMA. However, a quantitative composition analysis by EPMA confirms that some Sr is contained in the grain boundaries.

  Therefore, the grain boundaries include (1) a solid solution of Al-Ga-Sr oxide, (2) a solid solution of Al-Ga oxide and Sr oxide, and (3) a solid solution of Al-Ga-Sr oxide. In addition, it can be determined that Al, Ga, and Sr are present in any form of a solid solution of an Al—Ga-based oxide and an Sr oxide.

Example 3
FIG. 7 shows the X-ray diffraction results of the test pieces with various substitution amounts of Ca. In FIG. 7, when the X-ray diffraction pattern located at the top is m = 0 (test piece No. 43), below it is m = 0.05 (test piece No. 1), below it is m = 0.10. Case (test piece No. 2). Below that is m = 0.20 (test piece No. 4), and the lowest position is when m = 0.30 (test piece No. 6). Each specimen was calcined at 1300 ° C for 4 hours.

As is clear from FIG. 7, it can be seen that the diffraction peak becomes sharper from the upper pattern to the lower pattern. This indicates that the reactivity during calcination is improved with an increase in the amount of Ca substitution. That is, by replacing a part of Sr with Ca, the reactivity at the time of calcination can be improved. Conventionally, it has been difficult with a La-Al-Sr-Ti-based oxide dielectric ceramic, starting from 1200 ° C It is possible to calcine at a temperature of 1300 ° C.

According to this invention, the dielectric constant εr is near 39, the Qf ₀ value is 57,000 or more, and the temperature coefficient τf of the resonance frequency can be controlled in the range of −8 ppm / ° C. to 6 ppm / ° C. A dielectric ceramic composition for electronic devices having characteristics can be obtained, and it can cope with the downsizing and high performance required for portable terminal electronic devices in recent years.

It is a figure of the composition image and characteristic X-ray image which show the EPMA analysis result of the dielectric material ceramic composition for electronic devices of this invention. FIG. 2 is a schematic diagram showing BEI (composition image) of FIG. FIG. 2 is a schematic diagram showing a characteristic X-ray image of Al in FIG. FIG. 2 is a schematic diagram showing a characteristic X-ray image of Ga in FIG. FIG. 2 is a schematic diagram showing a characteristic X-ray image of Ti in FIG. FIG. 2 is a schematic diagram showing a characteristic X-ray image of La in FIG. It is a graph which shows the X-ray-diffraction result of the dielectric material ceramic composition for electronic devices of this invention.

Claims (2)

_{(1-x) (La 1} -y Ln y) (Al 1-z Ga z) O 3 -x (Sr 1-m Ca m) TiO 3 solid solution (where, Ln is Pr, Nd of one or two, x, y, z, and m satisfy the following values) as the main phase, and a solid solution of Al-Ga-Sr oxide or a solid solution of Al-Ga oxide and Sr oxide or Al- A dielectric ceramic composition for electronic devices in which a solid solution of Ga-Sr-based oxide and a solid solution of Al-Ga-based oxide and Sr oxide are present.
0.5 ≦ x ≦ 0.6, 0 <y ≦ 0.2, 0 <z ≦ 0.05, 0 <m ≦ 0.3 _{2. The} dielectric ceramic composition for an electronic device according to claim 1, wherein α-Al ₂ O ₃ is not substantially present at the grain boundary.

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