• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.863-866
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• 1999

(Ba,Sr)$TiO_3$ thin films have attracted groat interest as new dielectric materials of capacitors for ultra-large-scale integrated dynamic random access memories (ULSI-DRAMs) such as 1 Gbit or 4 Gbit. In this study, inductively coupled $BCl_3/Cl_2$/Ar plasmas was used to etch (Ba,Sr)$TiO_3$ thin films. RF power/dc bias voltage = 600 W/-250 V and chamber pressure was 10 mTorr. The $Cl_2/(Cl_2+Ar)$ was fixed at 0.2, the (Ba,Sr)$TiO_3$ thin films were etched adding $BCl_3$. The highest (Ba,Sr)$TiO_3$ etch rate is 480$\AA/min$ at 10 % $BCl_3$ adding to $Cl_2$/Ar. The characteristics of the plasmas were estimated using optical emission spectroscopy (OES). The change of Cl, B radical density measured by OES as a function of $BCl_3$ percentage in $Cl_2$/Ar. The highest Cl radical density was shown at the addition of 10% $BCl_3$ to $Cl_2$/Ar. To study on the surface reaction of (Ba,Sr)$TiO_3$ thin films was investigated by XPS analysis. Ion enhancement etching is necessary to break Ba-O bond and to remove $BaCl_2$. There is a little chemical reaction between Sr and Cl, but Sr is removed by physical sputtering. There is a chemical reaction between Ti and Cl, and Tic14 is removed with ease. The cross-sectional of (Ba,Sr)$TiO_3$ thin film was investigated by scanning electron microscopy (SEM), the etch slope is about $65\;{\sim}\;70$.

• Journal of the Korean Ceramic Society
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• v.23 no.2
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• pp.21-30
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• 1986

Pure submicron $SrTiO_3$ powders had been synthesized with chemical wet process that $5N-NH_4OH$ solution was sprayed into the mixed solution of $SrTiO_3$, $TiCl_4$ and $H_2O_2$ with $N_2$ carrier gas. The characteristic properties of powders obtained from this experiment were as follows. The optimum synthesis condition in reaction bath was above PH 8.5 and under $25^{\circ}C$ The particle size of precipitated SrTiO(OH) powders dried at 6$0^{\circ}C$ was under 0.01${\mu}{\textrm}{m}$ and uniform. Amorphous precipitated complex powders emitted adsorbed water at 15$0^{\circ}C$ less that and crystalline $SrTiO_3$powders was produced from calcining the complex at 30$0^{\circ}C$. Sintered body of SrTiO3 fired at 133$0^{\circ}C$ showed that relative dielectric constant was 228 at 1MHZ and bulk density was 4.73g/$cm^3$.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.85-87
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• 2002

The $(Ba_xBi_{0.6-x}Sr_{0.4})TiO_3$[x=0.1, 0.2, 0.3] ceramics were prepared by conventional mixed oxide method The structural properties of the $(Ba_xBi_{0.6-x}Sr_{0.4})TiO_3$[x=0.1, 0.2, 0.3] ceramics with the sintering temperature($1200^{\circ}C,\;1250^{\circ}C,\;1300^{\circ}C$) were investigated by XRD, SEM, EDS. Increasing the sintering temperature, the intensity of the $Ba_{0.5}Sr_{0.5}TiO_3$ (100), (110), (111), (200), (310) peaks and $SrBi_4Ti_4O_{15}$ (319), (040) peaks were increased. The gram of the $(Bi_{0.2}Ba_{0.4}Sr_{0.4})TiO_3$ ceramics sintered at $1250^{\circ}C$ were fine and uniform. Increasing the sintering temperature. the average gram size of the $(Bi_{0.2}Ba_{0.4}Sr_{0.4})TiO_3$ ceramics were decreased. The density of $(Bi_{0.1}Ba_{0.5}Sr_{0.4})TiO_3$ ceramics sintered at $1250^{\circ}C$ was 5.4524 [$g/cm^2$].

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1485-1487
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• 2002

The 0.96Mg$TiO_3$-0.04Sr$TiO_3$ ceramics with $V_2O_5$(5wt%) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature by XRD and SEM. According to the X-ray diffraction patterns of the 0.96Mg$TiO_3$-0.04Sr$TiO_3$ceramics with $V_2O_5$(5wt%), the ilmenite $MgTiO_3$ and perovskite $SrTiO_3$ structures were coexisted and secondary phase $MgTi_2O_5$ were appeared. Increasing the sintering temperature, the grain size was increased and three types of grains were exhibited: larger circular grain, small square grain and lapth-shaped grain. In the case of 0.96Mg$TiO_3$-0.04Sr$TiO_3$ ceramics with $V_2O_5$(10wt%), dielectric constant, quality factor and temperature coefficient of resonant frequency were $15.24{\sim}18.55$, $22,890{\sim}42,100$GHz, -24.5${\sim}$+2.414ppm/$^{\circ}C$, respectively.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.04b
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• pp.36.2-36.2
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• 2004

• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.79.2-79.2
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• 2004

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.363-366
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• 2004

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 mixed oxide method and sintered at $1425^{\circ}C{\sim}1500^{\circ}C$. According to XRD Patterns, hexagonal $Mg_4Ta_2O_9$ phase and cubic $SrTiO_3$ Phase 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, 82,596GHz and $-3.14ppm/^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.86-86
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• 2009

The $(Na_{0.5}K_{0.5})NbO_3-SrTiO_3$ ceramics were produced by the conventional solid-state sintering method, and their microstructure and electrical properties were investigated. All $(Na_{0.5}K_{0.5})NbO_3-SrTiO_3$ ceramic show dense and homogeneous structure without the presence of the rosette structure. The dielectric constant, loss and remanent polarization of $(Na_{0.5}K_{0.5})NbO_3-SrTiO_3$ ceramics were superior to those of single composition $(Na_{0.5}K_{0.5})NbO_3$

• Journal of the Korean Ceramic Society
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• v.22 no.3
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• pp.19-24
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• 1985

The phtoelectrochemical porperties of $Nb_2O_5$, $Sb_2O_3$ and $V_2O_5$ doped and pure $SrTiO_3$ ceramic electodes were investigated. Shapes of I-V and I-λ characteristics of the pure $SrTiO_3$ ceramic electrode are similar to those of SrTiO3 single crystal electorde ; the anodic current strats at -0.9V (vs. Ag/AgCI) in 1 N-NaOH aqueous solution and the photoresponse appears at a wavelength of about 390nm and the quantum efficiency is about 3.5% at wavelength of 390nm under 0.5V vs. Ag/AgCl. Photocurrents of $Nb_2O_5$, $Sb_2O_3$ and $V_2O_5$ doped electrodes and $V_2O_5$ doped ceramic electrode appears at wavelength of 390nm and 500nm respectively.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.180-182
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• 2004

Polycrystalline $BaTiO_3/SrTiO_3$ powder was prepared by sol-gel process and the multilayered thick films were prepared on the $Al_2O_3$ substrates by screen printing method. The films were sintered at $1400^{\circ}C$ for 2 hours in the air. The structural and dielectric properties were investigated, The X-ray diffraction (XRD) patterns indicate that the BST phase and porocity were formed in the interface of $BaTiO_3/SrTiO_3$ multilayered thick films. The dielectric constant and the dielectric loss of the BT/ST/BT/ST multilayered thick films were about 247 and 0.84% at 1MHz.