• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.344-345
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• 2006

In this study, in order to develop low temperature sintering piezoelectric transformer, $(Pb_{0.99-x}Ca_xSr_{0.01})Ti_{0.96}(Mn_{1/3}Sb_{2/3})_{0.04}O_3$ ceramic systems were fabricated using $Na_2CO_3-Li_2CO_3$ as sintering aids and investigated with the amount of Ca substitution. The piezoelectric transformer requires high electromechanical coupling factor $k_t$ and high mechanical quality factor $Q_{mt}$ for generating high output power At the ($PbCaSr)Ti(MnSb)O_3$ ceramics with 24mol% Ca substitution sintered at $900^{\circ}C$, electromechanical coupling factor $k_t$ and mechanical quality factor $Q_{mt}$ showed the optimal values of 0.504 and 1655 respectively, for thickness vibration mode multilayer piezoelectric transformer application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.1
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• pp.24-29
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• 2002

In this paper, the microstructure and the dielectric properties of Sr$\_$1-x/CaxTiO$_3$(0$\leq$x$\leq$0.2)-based grain boundary layer ceramics were investigated. The sintering temperature and time were 1420∼152 0$\^{C}$ and 4 hours in N$_2$ gas, respectively. The average grain size and the lattice constant were decreased with increasing content of Ca, but the average grain size was increased with increase of sintering temperature. The second phase foamed by the thermal diffusion of CuO from the surface leads to verb high apparent dielectric constant, $\xi$$\_$r/>50000 and low dielectric loss, tan$\delta$<0.05. X-ray diffraction patterns of Sr$\_$1-x/CaxTiO$_3$ exhibited cubic structure, and the peaks shifted upward and the peak intensity were decreased with x. This is due to the lattice contraction as Sr is replaced by Ca with a smaller ionic radius. The specimens treated thermal diffusion for 2hrs in 1150$\^{C}$ exhibited nonlinear current-voltage characteristic, and its nonlinear coefficient(a) was overt 7.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.21-24
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• 2010

The effects of mole ratio(A/B) m and Ti-ion on the dielectric properties and microstructure of the microwave dielectric ceramics $(Ca_{0.7}Sr_{0.3})_m(Ti_yZr_{1-y})O_3$ were investigated. Ti ions substituted on Zr-sites in these modified $CaZrO_3$ composition strongly affect the sintering density and microstructure of the fired ceramic body. With increasing the amount of Ti substituted on Zr-sites, the sintered density rapidly increased and the dense microstructure was obtained for the compositions having mole ratio of 1.01, whereas the sintered density and microstructure are nearly constant with the content of Ti-ion for the compositions having mole ratio of 0.99. With increasing the content of Ti ion, the curve of TCC (Temperature Coefficient of Capacitance) as a function of temperature rotated clockwise and satisfied the COG characteristics for both of compositions with mole ratio of 0.99 and 1.01. The content of Ti ion seems to be more effective than mole with respect to the controlling of firing and TCC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.21-24
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• 1993

The microstructure of the cubic perovskite [(Ba$\sub$85.5/ Ca$\sub$15.5)(Ti$\sub$60/ Mn$\sub$40/)O$_2$]-based dielectrics has been investigated. BCTM which control both A-site and B-site has less electrical characteristics than BaTiO$_3$. The dielectric factor was decreased and the dielectric loss factor was improved because BaMnO$_3$was formed in the solide reaction method.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.24-28
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• 2003

(Ba,Sr,Ca)TiO$_3$ powders, prepared by the sol-gel method, were mixed with organic binder and the BSCT thick films were fabricated by the screen printing techniques on alumina substrates. All the BSCT thick films, sintered at 1420$^{\circ}C$, showed the typical XRD patterns of a perovskite polycrystalline structure. The average grain sizes decreased with increasing amounts of ZrO$_2$, and the BSCT(40/40/20) thick films doped with 2wt% MnO$_2$ showed a value of 8$\mu\textrm{m}$. The thickness of thick films by four-cycle on printing/drying was approximately 951$\mu\textrm{m}$. The relative dielectric constant decreased with increasing Ca content and MnO$_2$ doping amount. The relative dielectric constant, dielectric loss and tunability of the BSCT(50/40/10) thick films doped with 2.0wt% ZrO$_2$ were 772, 0.184％ and 15.62%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.259-262
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• 1998

PbTi $O_3$ family ceramics can be used for the piezoelectric transformer using thickness extensional vibration mode because it is a material with the large anisotropy between electromechanical coupling factors $k_{t}$ and $k_{p}$. However, PbTi $O_3$ family ceramics have a difficult poling condition on account of its large anisotrophy. In this study, the structural and piezoelectric properties of (P $b_{0.76}$ $Ca_{0.24}$)[ $Ti_{0.96}$(M $n_{1}$3/S $b_{2/3}$)$_{0.04}$] $O_3$ system ceramics were investigated as a function of poling voltage in order to find the best poling condition.ion.n.n.ion.n.

• Transactions of Materials Processing
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• v.15 no.3 s.84
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• pp.213-219
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• 2006

To improve the strength of glass is being studied in order to contribute to weight saving of flat panel displays. Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness by the formation of a heterogeneous phase inside glass. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5\;and\;70SiO_2-10CaO-24Na_2O-10TiO_2$ glasses were irradiated to strengthen by crystallization using femto-second laser pulse. XRD, Nano-indenter and SEM etc., irradiation of laser pulse without heat-treated samples was analyzed. Samples irradiated by laser had higher value($4.4{\sim}4.56^*10-3Pa$) of elastic modulus which related with strength of glass than values heat-treated samples and these are $1.2{\sim}1.5$ times higher values than them of mother glass. This process can be applicable to the strengthening of thinner glass plate, and it has an advantage over traditional heat-treatment and ion-exchange method.

• Korean Journal of Materials Research
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• v.7 no.10
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• pp.872-876
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• 1997

(1-x)CaTi $O_{3}$-xLa(Z $n_{1}$2/ $Ti_{1}$2/) $O_{3}$의 마이크로 유전특성을 조사하였다. x가 증가함에 따라 비유전율과 공진주파수의 온도계수는 감소하였으며, Qㆍ $f_{0}$는 증가하였다. 그 결과 x=0.5인 (C $a_{0.5}$L $a_{0.5}$)( $Ti_{0.75}$Z $n_{0.25}$) $O_{3}$의 조성에서 $\varepsilon$$_{r}$=51, Qㆍ $f_{0}$=38,000 (at 7 GHz), $\tau$$_{f}$=+5ppm/$^{\circ}C$의 유전특성이 나타났다. (C $a_{0.5}$L $a_{0.5}$)( $Ti_{0.75}$Z $n_{0.25}$) $O_{3}$조성의 소결온도를 저하시키기 위하여 B $i_{2}$ $O_{3}$를 주조성으로한 소결체를 첨가하여 소결 및 유전특성을 조사하였다. 1wt% 0.76B $i_{2}$ $O_{3}$-0.24NiO가 첨가된 경우 소결온도는 15$0^{\circ}C$ 낮아졌으며, 비유전율 ($\varepsilon$$_{r}$), 공진주파수의 온도계수($\tau$$_{f}$), Qㆍ $f_{0}$가 각각 50+5ppm/$^{\circ}C$, 35,000인 마이크로파 유전특성이 얻어졌다. 또한 3wt%의 0.76B $i_{2}$ $O_{3}$-0.24NiO가 첨가된 경우 소결온도는 20$0^{\circ}C$ 저하되었고, 비유전율 ($\varepsilon$$_{r}$)과 공진주파수의 온도계수 ($\tau$$_{f}$)는 변하기 않았으나, Qㆍ $f_{0}$값이 38,000에서 25,000으로 저하되었다. 25,000으로 저하되었다.되었다.되었다.되었다.

• Korean Journal of Metals and Materials
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• v.47 no.3
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• pp.182-187
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• 2009

The molten salt electrolysis is applied to reduce titanium dioxide to titanium metal using calcium chloride as an electrolyte and the reaction mechanism of the reduction process is examined by analyzing the reaction products. The process conditions to obtain titanium metal for $900^{\circ}C$ correspond to 2.9~3.2 V and 24 hours. The reaction products for 2.9 V at $900^{\circ}C$ include irregular-shaped titanium oxides such as $Ti_4O_7$, $Ti_3O_5$ and $Ti_2O_3$ and polyhedral $CaTiO_3$. Using these microstructure analysis, the sequential reaction mechanism for the electrochemical reduction of titanium dioxide to titanium is proposed.

• Journal of the Korean Ceramic Society
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• v.18 no.2
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• pp.112-118
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• 1981

A study was made on the processing of domestic blast furnace slag by flotation and chemical purification for the use of slag as a raw material in making soda lime glasses. Feasibility study has been made for the use of reprocessing slag as a source material for both coloring and chemical components (such as CaO, $Al_2O_3$, MgO and etc.) in the glass making process. Chemical composition of chemically purified slags ranges; $SiO_2$ 34.5~37.5, $Al_2O_3$, 16.2~14.1, $Fe_2O_3$ 0.33~0.14, CaO 34.5~38.8, MgO 4.0~5.2, NmO 0.16~0.39, $TiO_2$ 0.23~0.35, S 0.08~0.42, ignition loss 3.3~8.4 and others 0.48~0.51%. It was found that either amber or greenish color could be easily obtained with the addition of salg up to 24%, however the slag addition to glass batches much impaired the transmitancy of glass products, thus a glass made with 7% slag addition showed 82% in transmitancy value at 510 nm.