Microwave dielectric properties of (1 - x)(Mg0.95Co0.05)TiO3–x(Na0.5La0.5)TiO3 ceramic system

Cheng-Liang Huang,Jhih-Yong Chen,Yen-Hsing Wang,Bing-Jing Li 한국물리학회 2009 Current Applied Physics Vol.9 No.6

The microstructures and the microwave dielectric properties of the (1 - x)(Mg0.95Co0.05)TiO3– x(Na0.5La0.5)TiO3 ceramic system were investigated. Two-phase system was confirmed by the XRD patterns and the EDX analysis. A co-existed second phase (Mg0.95Co0.05)Ti2O5 was also detected. The microwave dielectric properties are strongly related to the density and the matrix of the specimen. A new microwave dielectric material 0.88(Mg0.95Co0.05)TiO3–0.12(Na0.5La0.5)TiO3, possessing an excellent combination of dielectric properties: εr ~22.36, Q × f ~ 110,000 GHz (at 9 GHz), τf ~ 2.9 ppm/℃), is proposed as a candidate dielectric for GPS patch antennas. The microstructures and the microwave dielectric properties of the (1 - x)(Mg0.95Co0.05)TiO3– x(Na0.5La0.5)TiO3 ceramic system were investigated. Two-phase system was confirmed by the XRD patterns and the EDX analysis. A co-existed second phase (Mg0.95Co0.05)Ti2O5 was also detected. The microwave dielectric properties are strongly related to the density and the matrix of the specimen. A new microwave dielectric material 0.88(Mg0.95Co0.05)TiO3–0.12(Na0.5La0.5)TiO3, possessing an excellent combination of dielectric properties: εr ~22.36, Q × f ~ 110,000 GHz (at 9 GHz), τf ~ 2.9 ppm/℃), is proposed as a candidate dielectric for GPS patch antennas.

Control of Microwave Dielectric Properties in 0.42ZnNb₂O_(6)-0.58TiO₂ Ceramics by the Quantitative Analysis of Phase Transition

Kwon, Do-Kyun,Kim, Dong-Wan,Hong, Kug Sun 대한금속재료학회 2002 METALS AND MATERIALS International Vol.8 No.6

Phase constitutions of ZnNb₂O_(6)-TiO₂ mixture ceramics were significantly changed according to the sintering temperature. Phase transition procedures and their effect on the microwave dielectric properties of 0.42ZnNb₂O_(6)- 0.58TiO₂ were investigated using X-ray powder diffraction and a network analyzer. The fractions of the phases composing the mixture were calculated by measuring integral intensities of each reflection. The structural transitions in 0.42ZnNb₂O_(6)-0.58TiO₂ were interpreted as the association of two distinct steps: the columbite and rutile to ixiolite transition present at lower temperatures (900~950 ℃) and the ixiolite to rutile transition at higher temperatures (1150~1300 ℃). These transitions caused considerable variation of microwave dielectric properties. Importantly, tf was modified to around 0 ppm/℃ in two sintering conditions (at 925 ℃ for 2 hr and at 1300 ℃ for 2 hr), by the control of phase constitution.

BaTiO$_3$ 세라믹의 마이크로파 소성 및 전기적 특성

배강,김호기,Bai, Kang,Kim, Ho-Gi 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.11

적외선 광온도계(IR optical thermometer)와 PID 온도조절기에 의해 소성온도와 시간을 정밀하게 조절할 수 있는 마이크로파 소성장치를 사용하여 BaTiO3 시편을 소성하였다. 또한 마이크로파 소성중에 광섬유 온도계(optical fiber thermoneter)로 시편의 내부온도를 측정하여 같은 조건에서의 일반소성에 의한 시편과 소성특성을 비교한 결과, 소성시간에 따른 빠른 입성장속도과 큰 결정립경을 가졌으며, 온도에 따른 유전성질의 변화는 20~16$0^{\circ}C$의 측정범위에서 같은 경향을 보였다. The microwave sintered BaTiO3 samples were obtained by using the microwave sintering device which can precisely control the sintering temperature and the sinter time by using IR optical thermometer and PID temperature controller. During microwave sintering the internal temperature of samples were mesur-ed by the optical fiber thermometer to compare the sintering behaviors between microwave- and con-ventionally sintered ones. The former showed the faster rate of grain growth with sintering time and the larger grain size than the latter. Also they showed the similar pattern of dielectric properties with tem-perature changes from 2$0^{\circ}C$ to 16$0^{\circ}C$.

Zn-B-O 글라스 첨가에 의한 Ca[(Li_1/3Nb_2/3)_0.2Ti_0.8]O_3-δ 세라믹스의 마이크로파 유전특성

인치승,김시연,여동훈,신효순,남산,In, Chi-Seung,Kim, Shi Yeon,Yeo, Dong-Hun,Shin, Hyo-Soon,Nahm, Sahn 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.12

With trend of the miniaturization and the high-functionalizing of mobile communication system, low-loss microwave dielectric materials are widely used for high frequency communication components. These dielectric materials should be co-sintered with highly electric-conducting metal such as silver or copper for high-frequency and thick film process application. Sintering temperature of $Ca(Li_{1/3}Nd_{2/3})_{0.2}Ti_{0.8}]O_{3-{\delta}}$, which has excellent dielectric properties such as ${\varepsilon}_r$ above 40, quality factor ($Q{\cdot}f_0$) above 16,000 GHz, and TCF (temperature coefficient of resonant frequency) of $-20{\sim}-10ppm/^{\circ}C$, is reported as high as $1,175^{\circ}C$, so it could not be co-sintered with silver or copper. Therefore in this study, low-temperature melting glasses of Zn-B-O and Zn-B-Si-O systems were added to $Ca[(Li_{1/3}Nb_{2/3})_{0.8}Ti_{0.2}]O_{3-{\delta}}$ to lower its sintering temperature under $900^{\circ}C$ without losing excellency of dielectric properties. With 15 weight % of Zn-B-Si-O glass and sintered at $875^{\circ}C$, specimen showed density of $4.11g/cm^3$, ${\varepsilon}_r$ of 40.1, $Q{\cdot}f_0$ of 4,869 GHz, and TCF of $-5.9ppm/^{\circ}C$. With 15 weight % of Zn-B-O glass and sintered at $875^{\circ}C$, specimen showed density of $4.14g/cm^3$, ${\varepsilon}_r$ of 40.4, $Q{\cdot}f_0$ of 7,059 GHz, and TCF of $-0.92ppm/^{\circ}C$.

저온동시소성(LTCC)을 위한 결정화 유리(La₂O₃-B₂O₃-TiO₂계)와 BaNd₂Ti₅O₁₄ 세라믹을 이용한 마이크로파 유전체 특성

황성진,김유진,김형순 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.8

The LTCCs (Low-Temperature Co-fired Ceramics) are very important for electronic industry to build smaller RF modules and to fulfill the necessity for miniaturization of devices in wireless communication industry. The dielectric materials with sintering temperature $T_{sint}$<90$0^{\circ}C$ are required. In this study, BaO-N $d_2$ $O_3$-Ti $O_2$ (BNT : 20∼40 wt%) for ceramic materials and L $a_2$ $O_3$- $B_2$ $O_3$-Ti $O_2$ (LBT : 80∼60 wt%) for crystallizable glasses were used. The glass/ceramic composites were investigated for sintering behavior, phase evaluation, densities, interface reaction and microwave dielectric properties. It was found that the addition LBT glass frist significantly lowered the sintering temperature to below 90$0^{\circ}C$ and the densification with increasing addition LBT glass frist developed rapidly which was meant to be namely 90% of relative density. The sintered bodies ekhibited applicable dielectric properties, namely 15 for $\varepsilon$$_{r}$,, 10000 GHz for Q* $f_{0}$. The results suggest that the composites have good potential as a new candidate for LTCC materials. 무선 이동통신 산업에서 소형화와 RF모듈을 구현하기 위해 저온 동시 소성 세라믹(LTCC)기술이 부각되고 있다. LTCC용 재료는 90$0^{\circ}C$ 이하의 온도에서 소성이 되어야 한다 본 연구는 BaO-N $d_2$ $O_3$-Ti $O_2$ (BNT:20∼40wt%) 세라믹과 L $a_2$ $O_3$- $B_2$ $O_3$-Ti $O_2$ (LBT:80∼60wt%) 유리를 혼합하여 유리를 결정화시킴으로, 나타나는 부수적인 효과를 얻고자 하였다. 이에 소결 거동, 결정상 분석, 상대밀도 그리고 유전특성을 평가하였다 80wt% 유리의 첨가는 90%에 가까운 상대밀도를 갖는 복합체로서 15에 가까운 유전율과 10000GHz의 품질계수와 같은 우수한 유전특성을 보였다. 이와 같은 결과는 유리 결정화를 이용하여 LTCC용 유전체에 적용될 수 있는 가능성을 부여하였다.

Low Loss La5-xSrxTi4+xAl1-xO17 Ceramics for Microwave Dielectric Applications

Yaseen Iqbal,Raz Muhammad 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.3

La5-xSrxTi4+xAl1-xO17 (x = 0, 0.20, 0.25 and 0.30) ceramics were prepared through a mixed oxide solid state sintering route and characterized in terms of phase, crystal structure, microstructure and microwave dielectric properties. La5Ti4AlO17 exhibited reasonable relative permittivity εr ~ 42, a high quality factor Q×fo ~ 18906 GHz but the temperature coefficient of resonance frequency τf ~ −19 ppm/°C was too low for practical applications. In order to tune τf through zero, Sr was substituted for La which increased εr to 47.1, decreased Q×fo to 16678 GHz and decreased negative τf to −4.8 ppm/°C at x = 0.25. The observed decrease in negative τf may be due an increase in tolerance factor and hence change in tilt scheme of BO6 octahedra as a result of substitution of larger cations for smaller cations.

Low-temperature sintering and microwave dielectric properties of B₂O₃-added ZnO-deficient Zn₂GeO₄ ceramics for advanced substrate application

Ma, Xing-Hua,Kweon, Sang-Hyo,Im, Mir,Nahm, Sahn Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.14

<P><B>Abstract</B></P> <P>ZnO-deficient Zn<SUB>2-</SUB> <I> <SUB>x</SUB> </I>GeO<SUB>4-</SUB> <I> <SUB>x</SUB> </I> ceramics with 0.05 ≤ <I>x</I> ≤ 0.15 were synthesized because a ZnO secondary phase is formed in the stoichiometric Zn<SUB>2</SUB>GeO<SUB>4</SUB> ceramics synthesized using micrometer-sized ZnO and GeO<SUB>2</SUB> powders. The Zn<SUB>1.9</SUB>GeO<SUB>3.9</SUB> ceramic sintered at 1000 °C showed a homogeneous Zn<SUB>2</SUB>GeO<SUB>4</SUB> phase with good microwave dielectric properties: <I>ε<SUB>r</SUB> </I> of 6.8, <I>Q</I> × <I>f</I> of 49,000 GHz, and <I>τ<SUB>f</SUB> </I> of −16.7 ppm/°C. However, its sintering temperature was still too high for it to be used as an advanced substrate for low-temperature co-fired ceramic devices. Therefore, various amounts of B<SUB>2</SUB>O<SUB>3</SUB> were added to the Zn<SUB>1.9</SUB>GeO<SUB>3.9</SUB> ceramics to reduce their sintering temperature. Owing to the formation of a B<SUB>2</SUB>O<SUB>3</SUB>-GeO<SUB>2</SUB> liquid phase, these ceramics were well sintered at low temperatures between 925 °C and 950 °C. In particular, 15 mol% B<SUB>2</SUB>O<SUB>3</SUB>-added Zn<SUB>1.9</SUB>GeO<SUB>3.9</SUB> ceramic sintered at 950 °C showed promising microwave dielectric properties for advanced substrates without the reaction with an Ag electrode: <I>ε<SUB>r</SUB> </I> = 6.9, <I>Q</I> × <I>f</I> = 79,000 GHz, and <I>τ<SUB>f</SUB> </I> = −15 ppm/°C.</P>

Magnetodielectric Effect in Microwave-Sintered Ba<SUB>0.8</SUB>Sr<SUB>0.2</SUB>TiO₃ and Co<SUB>0.9</SUB>Ni<SUB>0.1</SUB>Fe₂O₄ Composite

Sagar M. Mane,Sachin A. Pawar,Dipali S. Patil,Seong Hun Lee,Jae Cheol Shin 한국진공학회(ASCT) 2020 Applied Science and Convergence Technology Vol.29 No.2

Composites constructed by combining ferroelectric and ferromagnetic materials are of significant interest owing to their multifunctional features and potential applications in multifunctional devices. Herein, the magnetodielectric effect of a composite containing ferroelectric Ba0.8Sr0.2TiO₃ (BST) and ferrite Co0.9Ni0.1Fe₂O₄ (CNFO) phases is investigated. This ferroelectric and ferrite composite is synthesized using the co-precipitation method followed by microwave sintering. The tetragonal crystal structure of BST and cubic structure of CNFO are confirmed using X-ray diffraction. All composite samples are characterized using nanoparticle tracking analysis. The measurements of dielectric constant (room temperature) and loss tangent as a function of frequency show an increase in the dielectric constant with an increase in the CNFO phase. The highest value of magnetodielectric coefficient, -40.13 %, is observed for the 60BST-40CNFO composite at 100 Hz, which decreases with an increase in the applied frequency.

Accurate Measurements of the Unloaded Q of a Dielectric-loaded High-Q $TE_{01{\delta}}$ mode Cavity Resonator with HTS Endplates

Kwon, H.J.,Hur, Jung,Lee, Sang-Young The Korean Superconductivity Society 1999 Progress in superconductivity Vol.1 No.1

Methods for mode identification and accurate measurements of the unloaded Q ($Q_0$) of a dielectric-loaded $TE_{01{\delta}}$ mode cavity resonator with HTS endplates are proposed. A resonator with a sapphire rod and $YBa_2Cu_3O_{7-x}$(YBCO) endplates was prepared and its microwave properties were studied at temperatures above 30 K. The $TE_{01{\delta}}$ mode $Q_0$ of the resonator, designed to work as a tunable resonator with variations in the gap distance (s) between the sapphire rod and the top YBCO, was more than 1000000 at s = 0 mm and at 30 K with the resonant frequency of 19.56 GHz. The $TE_{01{\delta}}$ mode $Q_0$ decreases as s increases for s < 2 mm until mode couplings between the $TE_{01{\delta}}$ mode and other modes appeared at s = 2 mm. Significant dependence of the $TE_{01{\delta}}$ mode $Q_0$ on the input and output coupling constants was also observed. Applications of the open-ended $TE_{01{\delta}}$ mode cavity resonator for a tunable resonator with a very high Q as well as a characterization tool for the surface resistance measurements of HTS films are described.

Inactivation of foodborne pathogens influenced by dielectric properties, relevant to sugar contents, in chili sauce by 915 MHz microwaves

Kim, Woo-Ju,Park, Sang-Hyun,Kang, Dong-Hyun Elsevier 2018 LWT- Food science and technology Vol.96 No.-

<P><B>Abstract</B></P> <P>The objective of this study was to investigate the effect of sugar content on dielectric properties of chili sauce, and inactivation efficiency when exposed to microwave energy. Heating history showed sugar content was an important factor influencing heating rate when chili sauce was exposed to microwave energy. Also, chili sauce of lower sugar content had a higher dielectric constant and dielectric loss factor. This trend was linked to inactivation efficiency of chili sauce inoculated with foodborne pathogens. As sugar content decreased, the time required to inactivate foodborne pathogen was reduced. Also, the inactivation efficiency of microwave heating was better since conventional heating took much longer to inactivate foodborne pathogens to under the detection limit. Also, our results showed that there was no significant difference in color, except for 25% and 40% sugar content exposed to 915 MHz microwave at 3.0 kW. Even though decreased water activity was observed, there was no significant difference between conventional heating and microwave heating at 1.5 kW and 3.0 kW. These results show not only that microwave heating can inactivate foodborne pathogens without generating significant quality change but also that the effect relies on dielectric properties associated with the sugar content of chili sauce.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sugar content influence dielectric properties and heating rate of chili sauce. </LI> <LI> Chili sauce with higher dielectric properties show higher inactivation efficiency. </LI> <LI> Higher dielectric properties and power of microwaves energy induce less quality change. </LI> </UL> </P>