• Korean Journal of Materials Research
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• v.13 no.6
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• pp.360-364
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• 2003

$Sr_{l}$ $\pm$x/$Bi_{2}$ $\pm$y/$Ta_2$ $O_{9}$ and $Sr_{l}$ $\pm$$Bi_{x}$ $2\pm$y$Nb_2$$O_{9}$ ceramics were prepared by a solid state reaction method. X-ray diffraction analysis indicated that single-phase of Bi-layered perovskite was obtained. According to Sr/Bi content ratio, Curie temperature( $T_{c}$), electromechanical factor($K_{p}$ ) and mechanical quality factor($Q_{m}$ ) were measured. The Curie temperature of SBN(SBT) rose from $414^{\circ}C$(314$^{\circ}C$) to $494^{\circ}C$(426$^{\circ}C$) when Sr/Bi content ratio was increased. In the case of Sr/Bi content ratio = 0.55/2.3, the maximum value of the mechanical quality factor $Q_{m}$ of SBT and SBN were obtained 3320 and 1010, respectively.

• Journal of Sensor Science and Technology
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• v.18 no.6
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• pp.456-461
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• 2009

Perovskite-structure $Sr(Ti_{1-x}Fe_x)O_3$ thick films, in which x is 0.4 or 0.6, were prepared by normal ceramic process on alumina substrate. Electrical resistance was measured as a function of thermal treatment condition including atmosphere, time, and temperature. The resistance of $Sr(Ti_{1-x}Fe_x)O_3$ films is lower than those of $SrTiO_3$ or $SrFeO_3$ films. The temperature coefficient of resistance over $550^{\circ}C$ was measured to be 0 for the $Sr(Ti_{1-x}Fe_x)O_3$ films after thermal treatment at $1100^{\circ}C$ in air. The sensing property of the films was also measured as a function of temperature and gas such as $O_2$, CO, $CO_2$, NO and $NO_2$. $Sr(Ti_{1-x}Fe_x)O_3$ films showed a good sensing property for $O_2$, but no sensing signal for CO, $CO_2$, NO and $NO_2$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.8
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• pp.17-23
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• 2002

The SrS:CuCl TFEL devices were fabricated by electron-beam deposition and the luminescent characteristics of the fabricated SrS:CuCl TFEL devices were studied. The SrS powder was used as the host materials and 0.05 ~ 0.6 at% of CuCl powder was added as the luminescent center. The deposition conditions of substrate temperature, electron beam current, and deposition rate were 500 $^{\circ}C$ , 20 ~ 40 mA, and 5 ~ 10 /sec, respectively The total thickness of the phosphor layer deposited was 6000 . The blue emission at low CuCl concentrations was observed from the luminescent centers of monomer, dimer, trimer, and tetramer, The bright greenish blue emission at high CuCl concentrations was observed from the dimer and trimer luminescent centers. The maxium luminance was observed from the SrS:CuCl TFEL devices doped with 0.2 at% of CuCl concentration and the threshold voltage, luminance(L$_{40}$ ), efficiency(η$_{20}$) and CIE coordinate obtained were 55 V, 728 cd/$m^2$, 0.49 lm/w, and (0.21, 0.33), respectively..

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.547-550
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• 2000

The (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were 125$0^{\circ}C$~135$0^{\circ}C$, 2hr., respectively. From the X-ray diffraction patterns, it was found that the perovskite SrTiO$_3$ and ilmenite MgTiO$_3$ structures coexisted in the (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics. The dielectric constant($\varepsilon$$_{r}$) was increased with addition of SrTiO$_3$. The temperature coefficient of resonant frequency($\tau$$_{f}$) was gradually varied from negative value to the positive value with increasing the SrTiO$_3$. The negative temperature coefficient of resonant frequency of the magnesium titanate was adjusted to near zero at x=0.036, where the dielectric constant, quality factor, and $\tau$$_{f}$ were 20.65, 95120, and +1.3ppm/$^{\circ}C$, respectively. The temperature stability of qualify factor in (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics increased as the amount of MgTiO$_3$./TEX>.

• Economic and Environmental Geology
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• v.31 no.2
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• pp.149-158
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• 1998

Volcanic rocks including rhyolitic tuff, rhyolite and welded tuff in the Bupyeong silver mine area form a topographic circular structure known as a resurgent caldera. Granitic rocks are emplaced inside and outside area of the circular structure. K-Ar dating and Nd-Sr isotope studies were carried out to invesitigate the origin and petrogenetic evolution of the rhyolitic and granitic magma in the Bupeong silver mine area. Whole rock K-Ar age ranges from 208 to 131 Ma for rhyolitic rocks. Radiometric ages for the granitic rocks are 167.6 Ma for pink feldspar biotite granite from inside granitic pluton of the circular volcanic body, 178.8 Ma for the Kimpo hornblende biotite granite and 111.8 Ma for the Songdo foliated granite from outside granitic plutons of the volcanic body. The radiometric age data indicates that the volcanic activities which are partly overlapped by granite plutonic activities in the Bupyeong mine area had recorded early Jurassic and early Cretaceous in age. Initial Sr and Nd isotopic ratios of the rhyolitic rocks ($^{87}Sr/^{86}Sr$=0.710~0.719 and $^{143}Nd/^{144}Nd$=0.5115~0.5118) are similar to those of granitic rocks ($^{87}Sr/^{86}Sr$=0.709~0.716 and $^{143}Nd/^{144}Nd$=0.5115~0.5116) from inside granite stock. This means that similar source materials of felsic magma responsibles for the Bupyeong volcanic rocks and inside plutonic rocks. Based on the Nd and Sr isotopic compositions, rhyolitic and granitic magmas in the Bupyeong area originated from the partial melting of the old continental crust which has Nd model age ranging from 1500 to 2900 Ma. This is analogous to those of the other Jurassic granitoids in South Korea.

• 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 [$g/cm^2$].

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.453-460
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• 2019

The SR-DCSK(Short Reference Differential Chaos Shift Keying) is a variant of DCSK that improves data transmission speed and energy efficiency without additional complexity. However, even when the reference signal of the optimum length is applied, the BER performance of the SR-DCSK is not better than that of the conventional DCSK. In this paper, we propose a scheme to improve the performance of SR-DCSK by applying two scale factors (scale coefficients) to the reference signal and the information signal, respectively. And the performance of the proposed method is analyzed by BER using Gaussian Approximation. Based on the derived BER expressions, we minimize the BER for a given system parameter to optimize the ratio of the two coefficients. Simulation results confirm that the BER of the proposed method is much improved over the SR-DCSK when we apply the optimal ratio of the two scale factors.

• ETRI Journal
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• v.45 no.5
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• pp.910-921
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• 2023

In this study, we designed a 6T-SRAM cell using 16-nm CMOS process and analyzed the performance in terms of read-speed latency. The temperaturedependent Cu and multilayered graphene nanoribbon (MLGNR)-based nanointerconnect materials is used throughout the circuit (primarily bit/bit-bars [red lines] and word lines [write lines]). Here, the read speed analysis is performed with four different chip operating temperatures (150K, 250K, 350K, and 450K) using both Cu and graphene nanoribbon (GNR) nano-interconnects with different interconnect lengths (from 10 ㎛ to 100 ㎛), for reading-0 and reading-1 operations. To execute the reading operation, the CMOS technology, that is, the16-nm PTM-HPC model, and the16-nm interconnect technology, that is, ITRS-13, are used in this application. The complete design is simulated using TSPICE simulation tools (by Mentor Graphics). The read speed latency increases rapidly as interconnect length increases for both Cu and GNR interconnects. However, the Cu interconnect has three to six times more latency than the GNR. In addition, we observe that the reading speed latency for the GNR interconnect is ~10.29 ns for wide temperature variations (150K to 450K), whereas the reading speed latency for the Cu interconnect varies between ~32 ns and 65 ns for the same temperature ranges. The above analysis is useful for the design of next generation, high-speed memories using different nano-interconnect materials.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.17 no.3
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• pp.146-154
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• 2024

In this paper, we present a convenient liquid crystal (LC) molecular alignment method using brush hairs as an alternative to the rubbing process in the LC display industry. Titanium strontium yttrium zirconium oxide (TiSrYZrO) solution was prepared using a sol-gel process, and the TiSrYZrO alignment film production and LC molecular alignment were integrated through a one-step brush coating process. As the curing temperature increased, the LC molecule alignment of the LC cell improved, and the formation of a physical surface anisotropic structure due to the shear stress caused by the movement of the brush hairs on the coating surface led to uniform alignment of the LC molecules. Uniform and homogeneous LC molecular alignment was confirmed through polarizing optical microscopy and pretilt angle measurement. Through thermal oxidation using X-ray photoelectron spectroscopy, the TiSrYZrO thin film well formed of metal oxide was confirmed and verified to have excellent optical transparency. From these results, it is expected that a convenient LC molecular alignment method using brush hairs as an alternative to the rubbing process will be a viable next-generation technology.

• Journal of the Korean Magnetics Society
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• v.13 no.1
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• pp.29-35
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• 2003

Anisotropic Sr-ferrites were prepared by the spark plasma sintering process (SPS). The Ferrite particles were oriented and densified during sintering process, and the anisotropic ferrites were manufactured at low sintering temperature and a remarkable short time processing by SPS method. It was showed that the anisotropy of ferrite particles at the specimen outer side was more higher than that at the specimen center, and it seems possible that the orientation of ferrite particles was related to DC current. Magnetic and physical properties of sintered Sr-ferrites are Br = 3.15 kG, iHc : 2.67 kOe, and density : 5.033 g/cm$^3$ when the samples were sintered for 8 minutes at 106$0^{\circ}C$.