KR970008711B1 - Microwave dielectric ceramics - Google Patents
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- KR970008711B1 KR970008711B1 KR1019940030096A KR19940030096A KR970008711B1 KR 970008711 B1 KR970008711 B1 KR 970008711B1 KR 1019940030096 A KR1019940030096 A KR 1019940030096A KR 19940030096 A KR19940030096 A KR 19940030096A KR 970008711 B1 KR970008711 B1 KR 970008711B1
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Abstract
Description
[발명의 명칭][Name of invention]
마이크로웨이브용 유전체 세라믹 조성물Dielectric Ceramic Composition for Microwave
[발명의 상세한 설명]Detailed description of the invention
[발명의 분야][Field of Invention]
본 발명은 민생용 및 산업용 전자기기에 사용되는 마이크로 웨이브 대역 부품용 소재, 적층 세라믹 커패시터, 전자파 장해(Electro-Magnetic Interference : EMI)용 유전체 필터 및 온도보상용 캐패시터 소재로서 유용한 세라믹 조성물에 관한 것으로서, 특히 유전율이 높고 공진주파수의 온도계수가 작으며, 품질계수(Qluality factor : Q)가 우수한 유전체 세라믹(Ceramic) 조성물에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ceramic compositions useful as materials for microwave band components, multilayer ceramic capacitors, dielectric filters for electromagnetic interference (EMI) and capacitors for temperature compensation, which are used in consumer and industrial electronic devices. In particular, the present invention relates to a dielectric ceramic composition having a high dielectric constant, a low temperature coefficient of resonant frequency, and an excellent quality factor (Q).
[종래의 기술][Prior art]
최근 자동차 전화, 휴대 전화, 코드리스 전화, 위성방송 수신기등의 무선통신수단이 범용화 됨에 따라 마이크로웨이브용 회로, 집적회로의 발전 등으로 마이크로웨이브 대역용 필터, 기판 및 전압조절 진동자(Voltage Controlled Oscillator : VCO)용 유전체 세라믹이 널리 이용되고 있다.Recently, as wireless communication means such as automobile telephone, cellular phone, cordless telephone and satellite broadcasting receiver have become widely used, the microwave band filter, substrate and voltage control oscillator (Voltage Controlled Oscillator: VCO) have been developed due to the development of microwave circuit and integrated circuit. ) Dielectric ceramics are widely used.
이러한 마이크로웨이브 유전체 세라믹은 주로 공진기(Resonator)로 이용되고 있는데, 여기에 사용되는 세라믹 조성물로는 BaO-Nd2O3-TiO2, BaO-Sm2O3-TiO2, Pbo-ZrO2-CaO 등 다양한 유전체가 이용되고 있다. 이중 BaO-Nd2O3-TiO2와 BaO-Sm2O3-TiO2계 세라믹은 유전율이 60-80 정도이고 품질계수가 1GHz에서 5000 정도이지만, 공진주파수의 온도계수(τf)가 매우 커서 실용상 큰 문제가 있다.The microwave dielectric ceramic is mainly used as a resonator, and the ceramic composition used herein includes BaO-Nd 2 O 3 -TiO 2 , BaO-Sm 2 O 3 -TiO 2 , Pbo-ZrO 2 -CaO Various dielectrics are used. BaO-Nd 2 O 3 -TiO 2 and BaO-Sm 2 O 3 -TiO 2 -based ceramics have a dielectric constant of about 60-80 and a quality factor of about 5000 at 1 GHz, but have a very high temperature coefficient of resonant frequency (τ f ). There is a big problem in practical use.
그리고, 일본에서 제안된 PbO-ZrO2-CaO계는 유전율이 90 이상으로 높은 반면 고주파에서 품질계수가 1000에서 3500 정도로 낮고 3GHz 이상의 고주파에서는 손실이 높아서 대역통과필터(Band Pass Filter : BPF) 및 전압조절 진동자 등의 부품손실을 높이는 단점이 있다.In addition, the PbO-ZrO 2 -CaO system proposed in Japan has a high dielectric constant of more than 90, but the quality factor at high frequencies is as low as 1000 to 3500, and the loss at high frequencies of 3GHz or more is high band pass filter (BPF) and voltage There is a disadvantage in that the loss of parts, such as adjustable oscillator.
이러한 고주파부품에 적용되기 위한 요구특성으로서 품질계수가 높아야 하며(예를 들어, 1GHz에서 500 이상), 조성을 변화시켜 공진주파수의 온도계수를 0ppm/℃ 중심으로 양(Positive) 또는 음(Negative) 방향으로 자유자재로 조절이 가능해야 한다.As a required characteristic to be applied to such high-frequency components, the quality factor should be high (for example, 500 or more at 1 GHz), and the composition of the high frequency components may be changed in positive or negative direction with the temperature coefficient of resonant frequency centered at 0 ppm / ℃. It should be freely adjustable.
또한, 공진기의 크기(λ/ε)를 작게 하기 위해서는 유전율이 큰 세라믹 소재가 필요하다.In addition, in order to reduce the size (λ / ε) of the resonator, a ceramic material having a large dielectric constant is required.
이러한 특성 개선을 목적으로 제조된 세라믹 조성물로서, 산화비스무스(BiO2O3) 및 산화납(PbO)의 첨가로 인하여 유전율의 향상을 보고한 BaO-Bi2O3-Nd2O3-TiO2및 BaO-PbO-Nd2O3-TiO2계 조성물이 제안된 바 있다(日本國 특개소 62-78154 및 63-112458 참조).As a ceramic composition prepared for the purpose of improving such properties, BaO-Bi 2 O 3 -Nd 2 O 3 -TiO 2 reported an improvement in permittivity due to the addition of bismuth oxide (BiO 2 O 3 ) and lead oxide (PbO). And BaO-PbO-Nd 2 O 3 -TiO 2 -based compositions have been proposed (see Japanese Patent Laid-Open Nos. 62-78154 and 63-112458).
이 조성물의 유전율은 80 이상, 품질계수는 4000~5500 정도로 보고되어 있다.The dielectric constant of this composition is reported to be 80 or more and the quality factor is about 4000-5500.
그러나, 이들 조성은 제조공정상 산화납 및 산화비스무스를 과량으로 첨가하기 때문에, 이들 첨가원소의 휘발로 인하여 균일한 조성제어가 어려우며, 이들 첨가제는 제조공정상 인체에 매우 유해한 원소로 알려져 있으며, 값비싼 산화니오디움이 필수적으로 사용되는 유전체 조성물이다.However, since these compositions add excessive amounts of lead oxide and bismuth oxide in the manufacturing process, it is difficult to control uniform composition due to volatilization of these additive elements, and these additives are known as very harmful elements to the human body in the manufacturing process, and expensive oxidation Nidium is an essential dielectric composition.
[본 발명에서 해결하고자 하는 문제점][Problem to solve in the present invention]
마이크로웨이브용 부품에 사용되기 위해서 요구되는 조건은, 고주파에서 유전체의 유전율이 커야하고 품질 계수도 5000 이상 되어야 하며, 공진주파수의 온도계수가 ±5ppm/℃로 낮아야 한다.The conditions required for use in microwave components are that the dielectric constant of the dielectric should be high at high frequencies, the quality factor should be more than 5000, and the temperature coefficient of the resonant frequency should be as low as ± 5 ppm / ° C.
이들 유전특성을 만족하는 것 외에 제조공정에서 요구되는 조건은 성분원소의 휘발로 인한 조성의 제어가 어려운 단점을 방지함으로써 품질저하를 방지하고, 제조공정상 인체에 유해한 원소인 납(Pb) 및 비스무스 성분원소들의 양을 줄임으로써 제조 조성성분을 안정적으로 제어하는데 있다.In addition to satisfying these dielectric properties, the conditions required in the manufacturing process prevent the disadvantages of difficult control of the composition due to volatilization of the component elements, thereby preventing quality deterioration, and lead (Pb) and bismuth components, which are harmful elements to the human body in the manufacturing process. It is to stably control the manufacturing composition by reducing the amount of elements.
[발명의 목적][Purpose of invention]
본 발명은 상술한 조건들을 감안하여 안출된 것으로서, 그 목적은 종래 유전체에 비해 휘발성이 적고 인체에 무해한 소결조제를 사용하여 제조원소의 조성비가 안정화 되고 낮은 제조원가로 제조가능하며, 고주파에서 유전율이 크고 품질계수가 높은 마이크로웨이브 유전체 세라믹 조성물을 제공하는데 있다.The present invention has been made in view of the above-described conditions, and its object is to use a sintering aid which is less volatile and harmless to the human body than a conventional dielectric, so that the composition ratio of the manufacturing element can be stabilized and manufactured at low manufacturing cost, and the dielectric constant is high at high frequency. To provide a microwave dielectric ceramic composition having a high quality factor.
[발명의 구성][Configuration of Invention]
본 발명은 산화바륨, 산화납, 산화니오디움, 산화세륨, 산화란탄 및 이산화티탄을 주성분으로 하는 유전체 세라믹 조성물로서, 여러 가지 실험을 수행한 결과, 다음과 같은 새로운 조성을 얻었다. 예를 들어, 본 발명은 제 1 성분으로 6~20mol%의 (Ba1-α·Pbα)0, 제 2 성분으로 10~20mol%의 (Nd2O3(1-β-γ)·CeO2(β)·La2O3(Υ)), 제 3 성분으로 60~70mol%의 TiO2로 구성된다.The present invention is a dielectric ceramic composition containing barium oxide, lead oxide, niobium oxide, cerium oxide, lanthanum oxide, and titanium dioxide as a main component. As a result of various experiments, new compositions are obtained as follows. For example, the present invention provides 6 to 20 mol% of (Ba 1 -α · Pbα) 0 as the first component and 10 to 20 mol% of (Nd 2 O 3 (1-β-γ) CeO 2 as the second component. (β) La 2 O 3 (Υ) ), and the third component is composed of 60 to 70 mol% of TiO 2 .
본 발명은 산화니오디움보다 가격이 저렴한 산화세륨 및 산화란탄을 산화니오디움 자리에 일부 치환하여, 유전율 및 품질계수를 증가시키고, 공진주파수의 온도계수를 0ppm/℃ 부근으로 근접시킨 조성을 얻을 수 있다.The present invention partially replaces cerium oxide and lanthanum oxide, which are less expensive than sodium oxide, in place of nitric oxide to increase the dielectric constant and quality coefficient, and obtain a composition in which the temperature coefficient of resonance frequency is close to 0 ppm / ° C. .
상기 조성물을 1250℃~1400℃ 범위의 소결온도와 2시간~4시간 동안 소결하여 제조된 본 발명의 유전체 세라믹은 90이상의 유전율과, ±10ppm/℃ 이내의 공진주파수 온도계수를 얻을 수 있고, 1GHz 공진주파수에서 5000 이상의 품질계수를 갖는다.The dielectric ceramic of the present invention prepared by sintering the composition at a sintering temperature in the range of 1250 ° C. to 1400 ° C. for 2 hours to 4 hours has a dielectric constant of 90 or more and a resonance frequency temperature coefficient within ± 10 ppm / ° C., which is 1 GHz. It has a quality factor of more than 5000 at the resonance frequency.
[실시예]EXAMPLE
이하, 본 발명의 바람직한 실시예를 보다 상세히 설명한다.Hereinafter, preferred embodiments of the present invention will be described in more detail.
본 발명은 산화바륨, 산화납, 산화니오디움 및 이산화티탄의 조성을 여러 차례 변화시키면서 미량의 산화세륨과 산화란탄을 첨가물로 하여 여러 가지 실험을 하였다.In the present invention, various experiments were carried out using a small amount of cerium oxide and lanthanum oxide as additives while varying the composition of barium oxide, lead oxide, niobium oxide and titanium dioxide.
즉, x(Ba1-α·Pbα)O-y(Nd2O3(1-β-γ)·CeO2(β)·La2O3(γ))-zTiO2조성물을 표 1과 같이 산화세륨을 첨가한 조성과 표 2와 같이 산화란탄을 첨가한 조성과, 표 3과 같이 산화세륨과 산화란탄을 함께 첨가한 조성을 크게 나누어 실험하였다.That is, x (Ba 1- αPb α ) Oy (Nd 2 O 3 (1-β-γ) CeO 2 (β) La 2 O 3 (γ) )-zTiO 2 composition was oxidized as shown in Table 1. Experiments were performed by dividing the composition of cerium, the composition of adding lanthanum oxide as shown in Table 2, and the composition of adding cerium oxide and lanthanum oxide together as shown in Table 3.
각 표에 열거한 조성과 같이 평량한 시료를 탈이온수와 함께 혼합한다.Mix the basal sample with deionized water, as listed in each table.
이때, 상기 산화바륨(BaO) 대신에 탄산바륨(BaCO3)을, 산화납(PbO) 대신에 삼산화납(Pb3O4)를 사용할 수도 있다.In this case, barium carbonate (BaCO 3 ) may be used instead of barium oxide (BaO), and lead trioxide (Pb 3 O 4 ) may be used instead of lead oxide (PbO).
혼합은 볼밀링 방법을 이용하며, 지르코니아볼과 플라스틱 단지를 이용한다.Mixing uses a ball milling method, zirconia balls and plastic jars.
건조된 파우더를 100℃ 이상에서 2시간 동안 하소를 실시하고, 폴리비닐알콜을 적정량 첨가하여 지르코니아 유발에서 혼합한다.The dried powder is calcined at 100 ° C. or higher for 2 hours, and an appropriate amount of polyvinyl alcohol is added and mixed in the zirconia trigger.
혼합된 재료는 금형과 유압프레스를 사용하여 직경 10mm 이상, 높이 5mm 이상의 원통형 시편으로 성형한다.The mixed material is molded into cylindrical specimens of at least 10 mm in diameter and 5 mm in height using a mold and hydraulic press.
성형시의 압력은 1.0ton/㎠ 이상이다.The pressure at the time of shaping | molding is 1.0 ton / cm <2> or more.
성형된 시편을 지르코니아 셋터(Setter) 위에 높고 공기분위기에서 1250℃ 이상의 고온으로 즉, 상기 각 표에 열거한 소결조건으로 전기로를 이용하여 소결한다.The molded specimen is sintered using an electric furnace at a high temperature above zirconia setter and in an air atmosphere at a temperature of 1250 ° C. or above, sintering conditions listed in each table.
소결을 수행한 시편은 하키-콜만(Hakki-Coleman)법으로 약 3GHz에서 유전율을 측정하였고, 개방형 공진기법으로 유전체의 무부하 Q를 측정하였다.The sintered specimens were measured for dielectric constant at about 3 GHz by the Hockey-Coleman method, and the no-load Q of the dielectric was measured by an open resonant method.
또, 공진주파수의 온도계수는 아래 (1)식에 의해 25℃의 온도에 대한 공진주파수를 기준으로 25℃에서 125℃의 온도범위에 대하여 구하였다.In addition, the temperature coefficient of the resonance frequency was calculated for the temperature range of 25 ° C to 125 ° C based on the resonance frequency with respect to the temperature of 25 ° C by the following equation (1).
…(1) … (One)
·f(125)=125℃에서의 공진주파수Resonant frequency at f (125) = 125 ° C
·f(25)=25℃에서의 공진주파수Resonant frequency at f (25) = 25 ° C
·△T=측정온도차이, 이 경우 125-(25)=100ΔT = measurement temperature difference, in this case 125- (25) = 100
이상의 방법으로 제작된 각 세라믹 유전체의 유전특성을 측정한 결과, 각 표에 요약된 바와 같이, 조성중 이산화티탄(TiO2)의 첨가량(z)이 증가함에 따라 최적소결 온도는 감소하고, 품질계수가 증가하는 효과를 얻을 수 있다.As a result of measuring the dielectric properties of each ceramic dielectric fabricated by the above method, as summarized in each table, the optimum sintering temperature decreases as the amount of titanium dioxide (TiO 2 ) added (z) increases and the quality factor An increasing effect can be obtained.
그러나, 이산화티탄이 75몰% 이상일 때는 공진주파수의 온도계수는 양(Positive)방향으로 크게 이동되어 실용상 사용하기가 어렵다.However, when titanium dioxide is 75 mol% or more, the temperature coefficient of the resonance frequency is largely shifted in the positive direction, making it difficult to use practically.
또한, 60몰% 이하이면 화학조성비가 적합하지 않아 유전체가 형성되지 않는다.In addition, if it is 60 mol% or less, a chemical composition ratio is not suitable and a dielectric will not be formed.
따라서, 본 발명의 실시예에서 바람직한 TiO2의 첨가량(z)은 약 60~75몰%임을 알 수 있다.Therefore, it can be seen that the preferred amount of addition (z) of TiO 2 in the embodiment of the present invention is about 60 to 75 mol%.
조성중 산화니오디움(Nd2O3)의 양이 증가함에 따라 품질계수가 증가하는 효과를 얻을 수 있으나, 적정소결 온도가 1400℃ 이상으로 높아지며, 20몰% 이상일 때는 공진주파수의 온도계수가 양방향으로 이동되는 단점도 있다.As the amount of niobium oxide (Nd 2 O 3 ) increases during the composition, the quality coefficient can be increased.However, the optimum sintering temperature is higher than 1400 ℃ and when the molar temperature is 20 mol% or more, the temperature coefficient of the resonance frequency moves in both directions. There are also disadvantages.
또한, 첨가량이 10몰% 이하이면 상대적으로 이산화티탄의 첨가량이 증가하므로 공진주파수의 온도계수가 양방향으로 이동된다.In addition, when the addition amount is 10 mol% or less, since the addition amount of titanium dioxide is relatively increased, the temperature coefficient of the resonance frequency is shifted in both directions.
따라서, 산화니오디움 성분의 바람직한 조성비는 약 10~20mol%이다.Therefore, the preferable composition ratio of the niobium oxide component is about 10-20 mol%.
조성중 산화납(PbO)의 첨가량이 증가함에 따라서 적정소결 온도가 낮아지고 유전율이 증가하는 효과가 있으나, 50몰% 이상 첨가하면, 유전율은 증가하나 산화납의 휘발로 인하여 조성조절에 어려움이 있고 품질계수가 저하되는 단점이 있다.As the amount of lead oxide (PbO) added in the composition increases, the appropriate sintering temperature is lowered and the dielectric constant is increased.However, when 50 mol% or more is added, the dielectric constant increases but it is difficult to control the composition due to volatilization of lead oxide and the quality factor There is a disadvantage that is lowered.
또한, 조성중 산화바륨의 양을 증가시키면 품질계수는 낮아지나, 공진주파수의 온도안정성을 얻을 수 있다.In addition, if the amount of barium oxide in the composition is increased, the quality factor is lowered, but temperature stability of the resonance frequency can be obtained.
그리고, 산화세륨(CeO2) 및 산화란탄(La2O3)의 양이 증가함에 따라 유전율과 품질계수가 증가하며, 적정 소결온도가 낮아짐을 알 수 있으나, 공진주파수의 온도계수가 양방향으로 이동된다.As the amount of cerium oxide (CeO 2 ) and lanthanum oxide (La 2 O 3 ) increases, the dielectric constant and quality coefficient increase, and the appropriate sintering temperature decreases, but the temperature coefficient of the resonance frequency moves in both directions. .
상기 조성에서 산화바륨(BaO) 대신에 탄산바륨(BaCO3)을 이용하여도 유전특성에는 큰 변화가 없으며, 산화납(PbO) 대신에 삼산화납(Pb3O4)을 이용하면 균일한 혼합이 이루어지며, 유전특성에는 큰 영향을 미치지 않는다.Even if barium carbonate (BaCO 3 ) is used instead of barium oxide (BaO) in the composition, there is no significant change in dielectric properties, and uniform mixing is achieved by using lead trioxide (Pb 3 O 4 ) instead of lead oxide (PbO). It does not have much influence on the dielectric properties.
동일한 조성에서 소결온도가 높아지면 유전율과 품질계수가 증가하며, 소결시간이 길어지면 유전율은 거의 변화가 없으나 품질계수가 약간 증가함을 알 수 있다.In the same composition, the higher the sintering temperature, the higher the dielectric constant and the quality factor. The longer the sintering time, the higher the dielectric constant is, but the quality factor is slightly increased.
서로 다른 조성비와 소결조건 하에서 제조된 각 시료의 유전특성결과를 표 1, 표 2 및 표 3에 요약하였다.Dielectric properties of each sample prepared under different composition ratios and sintering conditions are summarized in Table 1, Table 2 and Table 3.
[표 1]TABLE 1
산화세륨 첨가시 각 조성 및 제조조건과 그에 따른 유전특성Composition and manufacturing conditions and dielectric properties according to the addition of cerium oxide
(x+y+z=100)(x + y + z = 100)
[표2][Table 2]
산화란탄 첨가시 각 조성 및 제조조건과 그에 따른 유전특성Composition and manufacturing conditions and dielectric properties according to the addition of lanthanum oxide
(x+y+z=100)(x + y + z = 100)
[표 3]TABLE 3
산화세륨과 산화란탄 첨가시 각 조성 및 제조조건과 그에 따른 유전특성Composition and manufacturing conditions and dielectric properties according to the addition of cerium oxide and lanthanum oxide
(x+y+z=100)(x + y + z = 100)
[발명의 효과][Effects of the Invention]
이상 설명한 바와 같이 본 발명에 의하면, 낮은 제조원가를 가지며, 휘발성이 적고, 인체에 유해한 성분의 조성비를 줄여 안정화된 소결조제를 이용하여 상온에서 90이상의 유전율과 공진주파수의 온도계수가 평탄하며, Q×f가 5000 이상의 품질계수를 갖는 유전체를 얻을 수 있다.As described above, according to the present invention, the temperature coefficient of the dielectric constant and resonance frequency of 90 or more is flat at room temperature by using a sintering aid stabilized with low manufacturing cost, low volatility, and reduced composition ratio of harmful components to the human body. It is possible to obtain a dielectric having a quality factor of 5000 or more.
이들 유전체는 유전율 및 품질계수가 우수하기 때문에 마이크로웨이브 유전체를 사용이 가능하며, 공진주파수의 온계수가 ±10ppm/℃ 이내에 있는 유전체는 EMI 필터용 유전체 및 온도보상용 캐패시터로도 널리 이용할 수 있다.Since these dielectrics have excellent dielectric constant and quality factor, microwave dielectrics can be used, and dielectrics having a resonance temperature of within ± 10 ppm / ° C can also be widely used as EMI filter dielectrics and temperature compensation capacitors.
또한, 값비싼 산화니오디움(Nd2O3) 대신에 이보다 훨씬 값이 저렴한 산화세륨 및 산화란탄을 첨가함으로써 원소재 자체가 차지하는 가격비중을 낮춤으로써 제조원가를 절감할 수 있다.In addition, by adding much cheaper cerium oxide and lanthanum oxide instead of expensive sodium oxide (Nd 2 O 3 ), it is possible to reduce the manufacturing cost by lowering the weight ratio of the raw material itself.
더욱이, 산화비스무스를 첨가하지 않기 때문에 이들 성분의 휘발에 대한 문제점을 해결하여 일반 제조공정을 사용할 수 있으며, 인체에 유해한 원소의 사용을 줄일 수 있는 효과를 발휘한다.Furthermore, since no bismuth oxide is added, the problem of volatilization of these components can be solved, and thus a general manufacturing process can be used, and the use of an element harmful to the human body can be reduced.
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