• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.282-285
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• 1999

The (1-x)MgTiO$_3$-xSrTiO$_3$(x=0,0.1) ceramics were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature and composition ratio by XRD, SEM and DT-TGA. Increasing the sintering temperature from 130$0^{\circ}C$ to 1$600^{\circ}C$, second phase was decreased and grain size was increased. In the case of 0.9 MgTiO$_3$-0.1SrTiO$_3$ ceramics sintered at 130$0^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency were 22.61, 10,928(at 1GHz), +50.26ppm/$^{\circ}C$ , respectively.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.118-120
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• 2001

The $0.96MgTiO_3-0.04SrTiO_3+xLa(0{\sim}1.0wt%)$ ceramics were prepared by conventional mixed oxide method. The structural properties of $0.96MgTiO_3-0.04SrTiO_3+xLa(0{\sim}1.0wt%)$ ceramics with sintering temperature were investigated by the XRD and SEM. From the X-ray diffraction patterns, it was found that the perovskite $SrTiO_3$ and ilmenite $MgTiO_3$ structures were coexisted in the $0.96MgTiO_3-0.04SrTiO_3$ ceramics. The second phase of $Sr_{0.5}LaTi_2O_6$ was shown with addition of the $La_2O_3$. The dielectric constant(${\varepsilon}_r$), $Q{\times}f$ value and the temperature coefficient of the $0.96MgTiO_3-0.04SrTiO_3+0.2La$ ceramics were 21. 41, 39991, $-3.3ppm/^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.340-345
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• 2003

B $i_2$ $O_3$-Ti $O_2$ composite dielectric ceramics have been prepared by a conventional solid state ceramic route. The composite ceramics were prepared with starting materials of different origin and the microwave dielectric properties were investigated. The sintered ceramics were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, Raman and microwave methods. Structural and microstructural analyses identified two separate phases: Ti $O_2$(rutile) and B $i_2$ $Ti_4$0$_{11}$. The separate grains of titania and bismuth titanate were distributed uniformly in the ceramic matrix. The composition 0.88Ti $O_2$-0.12B $i_2$ $Ti_4$ $O_{11}$ was found to have a Q$\times$f of 9300 GHz (measured at a frequency of 3.9 GHz), a temperature coefficient of frequency, $\tau$$_{cf}$ near zero and a high relative permittivity, $\varepsilon$r of 83. The microwave dielectric properties were measured down to 20$^{\circ}$K K. The quality factor increased on cooling the ceramic samples.les.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1453-1455
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• 1998

$Ba(Mg,Ta)O_3-Ba(Co,Nb)O_3$ ceramics were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of 1500-$1575^{\circ}C$ for 5[hr.] in air. The crystal structure was investigated by the XRD. The microstructure of the ceramics were observed by SEM. The microwave properties of dielectric resonators were investigated as a function of composition and sintering temperature. $Ba(Mg,Ta)O_3-Ba(Co,Nb)O_3$ ceramics have a structure of complex perovskite type, and have peaks of (101),(102),(201),(202) and (212). In the case of the $0.7Ba(Mg,Ta)O_3-0.3Ba(Co,Nb)O_3$ ceramic resonator, dielectric constant, quality factor and temperature coefficient of resonant frequency(TCRF, ${\tau}_l$) were a good value of 26.5, 11.500 at 10[GHz] and -1.3[ppm/$^{\circ}C$] from $25^{\circ}C$ to $60^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.538-542
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• 2005

The structural and microwave dielectric properties of $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics with sintering temperature were investigated. All the sample of the $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics were prepared by conventional miked oxide method and the sintering temperature was $1425\~1500^{\circ}C$. The hexagonal phase of $Mg_4Ta_2O_9$ and the cubic phase of $SrTiO_3$ were coexisted. The porosity of $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics were reduced with increasing sintering temperature. In the case of $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics sintered at $1475^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency were 14.51, 82,596 GHz and $-3.14\;ppm/^{\circ}C$, respectively.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.566-570
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• 2015

$Bi_{0.5}Na_{0.5}TiO_3$ (BNT) based ceramics are considered potential lead-free alternatives for $Pb(Zr,Ti)O_3$(PZT) based ceramics in various applications such as sensors, actuators and transducers. However, BNT-based ceramics have lower electromechanical performance as compared with PZT based ceramics. Therefore, in this work, lead-free bulk $0.99[(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}]_{(1-x)}La_xTiO_3-0.01SrZO_3$ (BNBTLax-SZ, with x = 0, 0.01, 0.02) ceramics were synthesized by a conventional solid state reaction The crystal structure, dielectric response, degree of diffuseness and electric-field-induced strain properties were investigated as a function of different La concentrations. All samples were crystallized into a single phase perovskite structure. The temperature dependent dielectric response of La-modified BNBT-SZ ceramics showed lower dielectric response and improved field-induced strain response. The field induced strain increased from 0.17%_for pure BNBT-SZ to 0.38 % for 1 mol.% La-modified BNBT-SZ ceramics at an applied electric field of 6 kV/mm. These results show that La-modified BNBT-SZ ceramic system is expected to be a new candidate material for lead-free electronic devices.

• Journal of Electrical Engineering and information Science
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• v.3 no.1
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• pp.68-72
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• 1998

The photomachinable glass-ceramics of Ag and CeO2 doped Li203-SiO2 (LAS)glass system was investigated as a function of UV irradiation time. After the expose and the non-exposed samples were heated, they went under crystalline phase with DTA, SEM, TEM and XRD of normal/high temperature. In this work, crystalline phases, microstructure and dielectric properties were studied under the various time of UV irradiation and heat treatment.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1271-1273
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• 1994

In the field of the optics, precise machine, semiconducting processing, the micro-positioning actuators are required for the control of position in the submicron range. In this study, PNN-PZN-PZT ceramics were fabricated by solid state reaction. The structural, dielectric and electric properties were investigated for sintering condition. The specimen sintered for 1hr at 1,150($^{\circ}C$), had the highest density and dielectric contant.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.187-187
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• 1997

Silicon nitride is the most excellent materials among structural ceramics. It has been reported that fracture toughness was improved with adding second phase particles, whisker, fiber etc. However, containing of second phase particles enhanced fracture toughness, however flexural strength was degraded. As adding nanosize SiC particles into silicon nitride, the physical properties of fluxural strength, fracture toughness, the modulus of elasticity. In this study, 2wt% $Al_2$O$_3$ and 4 wt% $Y_2$O$_3$ were added into UBE E-10 and 0, 10, 20, 30, 40, 50 vol% nano-SiC powder (Sumitomo T1 powder) were added, respectively. It is hot pressed at 185$0^{\circ}C$ for 1 hour. Most of structural ceramics for engineering application are wear resistance. In this study, wear behaviors (in water) of silicon nitride with varying the amount of nano-size silicon carbide were investigated, and was compared to physical properties. Simultaneously wear mechanism will be found out.

• Advances in materials Research
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• v.2 no.3
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• pp.173-180
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• 2013

Lead-free complex perovskite ceramics $NaMeO_3$ ($Me{\equiv}Nb$, Ta) were synthesized using conventional solid state reaction technique and characterized by structural, FTIR and electrical (dielectric and ac conductivity) studies. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software. XRD analysis of the compound indicated the formation of single-phase orthorhombic structure with the space group Pmmm (47). Dielectric studies showed the diffuse phase transition at $394^{\circ}C$ for $NaNbO_3$ and $430^{\circ}C$ for $NaTaO_3$. Ac conductivity in both the compounds follows Jonscher's power law.