• Korean Journal of Materials Research
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• v.8 no.11
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• pp.1043-1047
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• 1998

The effect of CuO and CdO addition on the microwave dielectric properties of $BiNbO_4$, ceramics were investigated. As the content of CdO increased, sintered density and quality factor decreased. With increasing sintering temperature, both the dielectric constant and quality factor increased. In the case of specimen sintered at $960^{\circ}C$ with addition of 0.03 wt% of CuO and CdO, respectively. the microwave dielectric properties obtained were dielectric constant of 41.2, quality factor ($Q{\times}f_0$) of 6,500 (at 5.6GHz), temperature coefficient of resonant frequency of $3ppm^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.9
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• pp.459-463
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• 2004

In this study, the (l-x)$TiTe_3O_{8}$-x$MgTiO_3$ ceramics were investigated to obtain the improved dielectric properties of a high temperature stability and a sintering temperature of less than $900^{\circ}C$ which was necessary for the LTCC. According to the X-ray diffraction patterns of the (l-x)$TiTe_3O_{8}$-x$MgTiO_3$(x=0∼1) ceramics, the columbite structure of $TiTe_3O_{8}$ and ilmenite structure of $MgTiO_3$ were coexisted. Increasing the $MgTiO_3$ mole ratio(x), the density and dielectric constant were decreased and temperature coefficient of resonant frequency was moved to the negative direction and the quality factor was increased. In the case of the 0.6$TiTe_3O_{8}$-0.4$MgTiO_3$ ceramics sintered at $830^{\circ}C$ for 3hr., the microwave dielectric properties were $\varepsilon_{\gamma}$=29.3, Q${\times}$$f_{\gamma}$=39.600GHz and $\tau$$_{f}$=+9.3ppm/$^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.843-846
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• 2000

The (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.02∼0.08) ceramics were fabricated by conventional mixed oxide method. The sintering temperature and time were 1250$^{\circ}C$∼1400$^{\circ}C$, 2hr., respectively. The structural and microwave dielectric properties were investigated by varying sintering temperature and composition ratio. In the (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.02) ceramics, the cubic SrTiO$_3$and hexagonal MgTiO$_3$phases were coexisted. The dielectric constant was increased and the temperature coefficient of resonant frequency( $\tau_f$) was decreased with addition of SrTiO$_3$. The temperature coefficient of resonant frequency($\tau_f$) was gradually varied from negative value to positive value with increasing the SrTiO$_3$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.337-341
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• 2021

Phase evolution, thermal and microwave dielectric properties of cordierite-Al₂O₃ composite were investigated. As the content of Al₂O₃ increased, mullite, sapphirine, and spinel were formed as secondary phases, implying that cordierite may be decomposed by the reaction with Al₂O₃. All sintered specimens exhibited dense microstructures. The densification occurred through liquid phase sintering. As the content of Al₂O₃ increased, the thermal expansion coefficient and the dielectric constant increased, whereas the quality factor decreased. The thermal expansion coefficient, the dielectric constant, and the quality factor of the 90 wt% cordierite 10 wt% Al₂O₃ composite sintered at 1,425℃ were 2.9×10^-6 K^-1, 5.1, and 34,844 GHz, respectively.

• Journal of Magnetics
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• v.2 no.1
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• pp.25-27
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• 1997

Ferrite tile absorber is of great concern for the application to anechoic chambers due to the growing demand of EMI or EMC measurements. This paper investigates the magnetic, dielectric and microwave absorbing properties of a Ni-An ferrite for the purpose. A design chart was constructed with the solutions of impedance-matching equation in the radio frequencies (30 MHz - 1 GHz). The material parameters for zero-reflection are predicted from the chart. The magnetic and dielectric properties of sintered Ni-Zn ferrite is found to be well suited for this requirements. A superior microwave absorbing properties (frequency band and absorber thickness) of the samples are demonstrated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.648-651
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• 2004

Pb0.5Sr0.5TiO3(PST) thin films were deposited on the LaNiO3 (LNO(100))/Si and Pt/Ti/SiO2/Si substrates by the alkoxide-based sol-gel method. Structural and dielectric properties of PST thin films for the tunable microwave device applications were investigated. The PST films, which were directly grown on the Pt/Ti/SiO2/Si substrates showed the random orientation. For the LNO/Si substrates, the PST thin films exhibited highly (100) orientation. Compared with randomly oriented films, the highly (100)-oriented PST thin films showed better dielectric constant, tunability, and figure of merit (FOM). The dielectric constant, tunability, and FOM of the highly (100)-oriented PST thin film increased with increasing annealing temperature due to the decrease in lattice distortion. The differences in dielectric properties may be attributed to the change in the film stress and the in-plane oriented Polar axis depending on the substrate was used. The dielectric constants, dielectric loss and tunability of the PST thin films deposited on the LNO/Si substrates measured at 1 MHz were 483, 0.002, and 60.1%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.288-289
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• 2006

We studied the effect of sol-gel processing and sintering temperature on the microwave properties of $MgCo_2(VO_4)_2$ system(MCV) which is applicable to LTCC(low-temperature cofired ceramics). The MCV was synthesized by sol-gel process using solution that contains precursor molecules for Mg, Co, and V. SEM analysis shows that the average particle size is ${\sim}1{\mu}m$ and size distribution is very uniform compared to the one prepared by conventional solid-state reaction process. Highly dense samples were obtained at the sintering temperature range of $750^{\circ}C{\sim}930^{\circ}C$. The maximum $Q{\times}f_0$ value of 55,700GHz, dielectric constant(${\varepsilon}_r$) of 10.41 and temperature coefficient(${\tau}_f$) of $-85ppm/^{\circ}C$ was obtained at the sintering temperature of $930^{\circ}C$. The superior microwave properties of sol-gel processed MCV relative to conventional solid-state reaction processed one is remarkable especially at lower sintering temperatures such as $750^{\circ}C$ and $800^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.386-389
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• 2001

In this study, development of a new LTCC material using non-glassy system was attempted with repsect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, $ZnWO_4$ was turned out the suitable LTCC material. $ZnWO_4$ can be sintered up to 98% of full density at $1050^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and $-70ppm/^{\circ}C$, respectively. In order to modify the dielectric properties and densification temperature, $B_{2}O_{3}$ and $V_{2}O_{5}$ were added to $ZnWO_4$. 40 mol% $B_{2}O_{3}$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to $-7.6ppm/^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of $V_{2}O_{5}$ in $ZnWO_{4}-B_{2}O_{3}$ system enhanced liquid phase sintering. 0.1 wt% $V_{2}O_{5}$ addition to the $0.6ZnWO_{4}-0.4B_{2}O_{3}$ system, reduced the sintering temperature down to $950^{\circ}C$. Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and $-21.6ppm/^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.386-389
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• 2001

In this study, development of a new LTCC material using non-glassy system was attempted with respect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, ZnWO$_4$ was turned out the suitable LTCC material. ZnWO$_4$ can be sintered up to 98% of full density at 105$0^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and -70ppm/$^{\circ}C$, respectively In order to modify the dielectric properties and densification temperature, B$_2$O$_3$ and V$_2$O$_{5}$ were added to ZnWO$_4$. 40 mol% B$_2$O$_3$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to -7.6ppm/$^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of V$_2$O$_{5}$ in ZnWO$_4$-B$_2$O$_3$ system enhanced liquid phase sintering. 0.lwt% V$_2$O$_{5}$ addition to the 0.6ZnWO$_4$-0.4B$_2$O$_3$ system, reduced the sintering temperature down to 95$0^{\circ}C$ Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and -21.6ppm/$^{\circ}C$ respectively.ively.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.394-398
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• 1998

$Pb_{1-x}Sr_x(Mg-{1}2}W_{1}2})O_3$$ ceramics for application in the microwave frequency range were investigated by dielectric constant and X-ray diffraction measurements. The dielectric constant curves showed two concentration dependent characteristics in the $$Pb(Mg-{1}2}W_{1}2})O_3$-rich$ region. As the Sr constant further increases to x=0.3 the dielectric curve levels off. In the concentration range between x=0.4 and x=1 in which dielectric constant dependence on temperature is negligible, it decreases and Qf value increases in the microwave frequency with increasing Sr. The temperature coefficient (${\tau}_{\varepsilon} $) of the dielectric constant changes from the negative to positive value between x=0.9 and x=1. The dielectric constant, Qf and $\tau\varepsilon$ are correlated with tolerance factor(t). From the X-ray diffraction results for $0.1{\le}x{\le}1$ the cell parameter is found to decrease as x increases and B-site ordering is observed in all the composition ranges.