• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.6
• /
• pp.229-234
• /
• 2018

The glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system was synthesized by using $ZrO_2$, $ZrSiO_4$, $ZrOCl_2$ and $Zr(SO_4)_2$, which is a raw material of Zr serving as a nucleation agent. It was confirmed that Avrami parameter of these four glasses is over 3 for bulk crystallization. The glass synthesized by $ZrOCl_2$, and $Zr(SO_4)_2$ showed high melting quality during the melting process. It is also observed that the Zr component is uniformly distributed in the glass. Various characterizations was evaluated, including composition analysis and bending strength.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.4
• /
• pp.532-538
• /
• 1998

Emerald ($3BeO{\cdot}Al_2O_3{\cdot}6SiO_2:Cr^{3+}$) single crystal was grown by temperature gradient reflux method with using Korean natural beryl. The flux of lithium-molibudenium-vanadium oxide system was made by means of mixing the 2 sort of flux which were differently melted $Mo_3-Li_2O$ and $V_2O_5-Li_2O$ each other. The optimum composition of flux was 3 mole ratio of molibudenium. vanadium oxides to lithium oxide ($(MoO_3+V_2O_5)/Li_2O$), flux additives were substituted more less then 0.2 mole% of $K_2O$ or $Na_2O$ to the $Li_2O$ amount. The melting concentration of mixing beryl material was 3~10% content to the flux, that of $Cr_2O_3$ color dopant was 1% to the beryl amount. In the crystal growing apparatus with temperature gradient in the 3 zone furnace which was separated into the block of melt, growth and return, the solution have got to circulate continuously between $1100^{\circ}C$ and $1000^{\circ}C$ in steady state. When thermal fluctuation was treated to during 2 hrs once on a day at 950~$1000^{\circ}C$ in growth zone, the supersaturation solution was maintained, controled and emerald single crystal can be grown large crystal which was prevented from the nucleation of microcrystallite. The preferencial growth direction of hexagonal columnar emerald single crystal was the c(0001) plane of botton side and vertical to the m(1010) plane of post side.

• Korean Journal of Optics and Photonics
• /
• v.14 no.6
• /
• pp.657-662
• /
• 2003

Optimum Hamming apodized acousto-optic 2${\times}$2 add/drop multiplexers, using SiO$_2$ film loaded acoustic waveguide with angular offset to the Ti:LiNbO$_3$ waveguide, were fabricated. The four-port device consists of two input waveguides, a polarization beam splitter (PBS), two polarization conversion/acoustooptic tuning waveguide sections, a second PBS and two output waveguides. Insertion loss <7.1 ㏈ has been obtained and side-lobe of -19 ㏈ for -32 ㎽ RF driving power has been realized. Add/drop performance has been confirmed and a linear tuning rate of 8.1 nm/MHz and a 3 ㏈ spectral width of -1.5 nm were demonstrated.

• Journal of the Korean Ceramic Society
• /
• v.25 no.5
• /
• pp.431-436
• /
• 1988

The properties of scid-resistance to boiling HCl, thermal expansion coefficient and softening temperature of mother glass and glass-ceramic of LAS systems were investigated at the contents of SiO2 varing from 57 to 67wt%. The nucleation and growth of crystalline phase of LAS compositions were carried out at 50$0^{\circ}C$ and $700^{\circ}C$. The crystalline phase jconsists of lithium alumino silicate, lithum meta silicate, lithium disilicate, $\alpha$-crystobalite and $\alpha$-quartz. Lithium alumino silicate(virgilite) is the major crystalline phase in the glass ceramics. The degree of acid resistant property was increased in proportion with the silica content for both glass and ceramics. Glass-ceramic gives lower acid-resistance and thermal expansion coefficient while softening temperature shows higher for glass-ceramic than for mother glass.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.6
• /
• pp.517-523
• /
• 2008

The microwave dielectric properties of $LiNb_3O_8-TiO_2$ based ceramics with low firing agents, CuO, $Bi_2O_3$, $B_2O_3$, $SiO_2$, $TiO_2$, were investigated to improve the sintering condition for the LTCC system. According to the X-ray diffraction and SEM, the ceramics of $LiNb_3O_8-TiO_2$ with low firing agents showed no significant second phases within a range of experiments, and fine microstructures. By adding the low firing agents, the sintering temperature decreased from $1200^{\circ}C$ to $925^{\circ}C$. Based on the results of electrical measurements, the $LiNb_3O_8-TiO_2$ ceramics showed a promising microwave dielectric properties for LTCC applications, those are ${\varepsilon}_r$ (dielectric constant) = 44, Q f (quality factor) = 18000, and ${\tau}_f$ (the temperature coefficient of resonant frequency) = $-1.5\;ppm/^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.134-137
• /
• 2004

새로운 리튬 2차전지용 양극활물질인 Li[NiMnCo]O2를 간단히 합성할 수 있는 방법과 Si의 doping에 의해 그 특성을 향상하였다. 원하는 당량비의 Li, Ni, Co, Mn의 nitrate를 고순도의 에탄올에 용해하고 여기에 Si의 원료물질로서 poly(methyl phenyl siloxane)을 원하는 양(전체 전이금속 이온의 $2{\sim}10\;mol%$)만큼 첨가한 후 약 30분 정도 교반하였다. 이 용액을 약 $70{\sim}80^{\circ}C$ 정도의 온도에서 고점도의 진흙 상태가 될 정도로 가열하고 $450{\sim}500^{\circ}C$의 온도에서 약 5시간 정도 열처리 하여 유기물이 없는 상태의 전구체를 제조하였다. 이 전구체를 분말형태로 분쇄하고 $600{\sim}650^{\circ}C$ 정도의 온도에서 3시간, $900{\sim}950^{\circ}C$ 정도의 온도에서 5시간 연속적으로 열처리 하여 최종 활물질을 제조하였다. 이렇게 제조된 활물질은 175mAh/g 정도의 높은 비용량을 나타내었으며 4.5V 충전 조건에도 우수한 수명특성을 나타내었다. Si이 doping되지 않은 활물질에 비해 Si이 doping된 물질은 율특성, 수명특성에서 보다 우수한 특성을 나타내었는데 이것은 층상구조 활물질의 격자상수 증가와 impedance 증가 억제에 기인한 것으로 분석되었다.

• Korean Journal of Acupuncture
• /
• v.21 no.1
• /
• pp.175-199
• /
• 2004

Objectives : To study acupuncture and moxibution treatments for stomatopathy( aphthae, oral ulceration, mycolic stomatitis, halitosis, thirst, bitter) the ancient and the present literatures were reviewed. Methods : We've got compared and analyzed 55 kinds of literatures. Results and Conclusions : 1. The acupuncture meridians used frequently for stomatopathy were $Su-yangmy\bar{o}ng-Taejang-ky\bar{o}ng(LI),\;Chok-yangmy\bar{o}ng-Wi-Ky\bar{o}ng(S),\;Immaek-Ky\bar{o}ng(CV)$. 2. The acupoints used frequently for aphthae were $Sungjang(CV_{24}),\;Yomchon(CV_{23}),\;Hapkok(LI_4),\;Nogung(P_8),\;Chok-samni(S_{36}),\;Hyopko(S_6),\;Sugu(GV_{26})$. 3. The acupoints used frequently for oral ulceration were $Hapkok(LI_4),\;Nogung(P_8),\;Chok-samni(S_{36}),\;Kokchi(LI_{11}),\;Sotaek(SI_1),\;Pisu(B_{20}),\;Wisu(B_{21}),\;Samgan(LI_3),\;Yomchon(CV_{23}),\;Chichang(S_4)$. 4. The acupoints used frequently for mycolic stomatitis were $Hapkok(L_4),\;Chichang(S_4),\;Hyopko\;(LI_4),\;Sungjang(CV_{24}),\;Samumgyo(SP_6)$. 5. The acupoints used frequently for halitosis were $Naejong(S_{44}),\;Chok-samni(S_{36}),\;Chung-wan\;(CV_{12}),\;Sang-wan(CV_{13}),\;Hawan(CV_{10}),\;Kongson(SP_4),\;Wisu(B_{21}),\;Nogung(P_8),\;Sugu(GV_{26}),\;Sungjang(CV_{24})$. 6. The acupoints used frequently for thirst were $Sosang(L_{11}),\;Sangyang(LI_1),\;Sotaek(SI_1),\;Kwanch'ung(TE_1),\;Ch'\bar{o}kt'aek(L_5),\;T'ae-gye(K_3),\;Kokt'aek(P_3),\;Sugu(GV_{26}),\;Samgan(LI_3),\;Igan(LI_2),\;T'aech'ung(Liv_3),\;Sojangsu(B_{27})$. 7. The acupoints used frequently for bitter were $Yangn\bar{u}ngch'\bar{o}n(G_{34}),\;Hy\bar{o}njong(G_{39}),\;Kwanch'ung(TE_1),\;Tamsu(B_{19}),\;Chokkyu\bar{u}m(G_{44}),\;Y\bar{o}n-gok(K_2),\;Shinmun(H_7),\;Chok-Samni(S_{36})$.

• Journal of the Microelectronics and Packaging Society
• /
• v.6 no.4
• /
• pp.35-39
• /
• 1999

The $Li_2O-MgO-MgF_2-SiO_2$glasses with addition of $B_2O_3$ were investigated in order to make glass-ceramics for low temperature firing substrate. Glasses were made by melting at $1450^{\circ}C$ in the electronic furnace and crystallized at $750^{\circ}C$. The crystal phases were polycrystalline of lithium boron fluorphlogopite and lithium fluorhectorite. The crystal shape was chanced to granule type from needle type with increasing $B_2O_3$ content. Average particle size of the glass-ceramics after water swelling was 3.77$\mu\textrm{m}$. The optimum sintering temperature and sintering shrinkage of the substrate were $900^{\circ}C$ and 13.4%, respectively.

• Journal of the Korean Ceramic Society
• /
• v.29 no.12
• /
• pp.935-941
• /
• 1992

The LAS system with good thermal properties has a narrow range of firing and sintering temperature near the melting point. So it is difficult to sinter LAS to dense sintered body. In this study, the petalite (Li2O.Al2O3.8SiO2) with good thermal properties, was taken as a base composition, and zironia was added in this composition to broaden the firing range, increase the mechanical strength, and control the thermal expansion. The thermal and mechanical properties were investigated. The results are as follows; 1. Zirconia phase was formed in LAS matrix and apparent porosity was decreased from 0.9% to 0.5%, and the mechanical strength was kincreased from 112 MPa to 190 MPa, by the densification of body. 2. The composition Li2O.Al2O3.8SiO2 has a negative thermal expansion, but the thermal expansion was changed from negative to positive with the densification and the increase of amount of synthesized zircon phase which had positive thermal expansion. The coefficient of thermal expansion, with the increase of the amount of additives, was low as -0.74~9.06$\times$10-7/$^{\circ}C$ in 20~$600^{\circ}C$, and 7.95~20.13$\times$10-7/$^{\circ}C$ in 20~80$0^{\circ}C$. 3. The mechanical strength of LZ15 (added with ZrO2.SiO2 15 wt%) composition thermal-shocked was stable in the temperature range of 0~$600^{\circ}C$, but rapidly decreased due to the increase of thermal expansion above $600^{\circ}C$.

• Journal of the Korean Vacuum Society
• /
• v.11 no.4
• /
• pp.230-234
• /
• 2002

Metal-ferroelectric-semiconductor(MFS) capacitors by using rapid thermal annealed $LiNbO_3$/Si structures were successfully fabricated and demonstrated nonvolatile memory operations of the MFS capacitors. The C-V characteristics of MFS capacitors showed a hysteresis loop due to the ferroelectric nature of the $LiNbO_3$thin film. The dielectric constant of the $LiNbO_3$film calculated from the capacitance in the accumulation region in the capacitance-voltage(C-V) curve was about 25. The gate leakage current density of MFS capacitor using a platinum electrode showed the least value of $1{\times}10^{-8}\textrm{A/cm}^2$ order at the electric field of 500 kV/cm. The minimum interface trap density around midgap was estimated to be about $10^{11}/cm^2$.eV. The typical measured remnant polarization(2Pr) value was about 1.2 $\mu\textrm{C/cm}^2$, in an applied electric field of $\pm$ 300 kv/cm. The ferroelectric capacitors showed no polarization degradation up to about $10^{10}$ switching cycles when subjected to symmetric bipolar voltage pulse in the 500 kHz.