• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.248-251
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• 1999

The microwave dielectric properties of The Dielectric Properties of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ (A = Sr, Ca, x = 0, 0.2 ,0.4 ,0.6, 0.8, 1.0) were investigated. In composition of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O, densities are decreased with increasing x values. Grain sizes are decreased with Sr content and Increased with Ca content. The hexagonally ordered superstructure was observed in $Ba_{1-x}$Sr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the intensity of superlattice increased with x value. In $Ba_{1-x}$Cr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the additional diffraction patterns were shown. The highest value of $\varepsilon$$_{r}$ was shown in x=0.2 of BCMN systems and the value was 41.9. The highest Q$\times$f was shown in x=0.2 of BSMN systems and the value was 68,000. $\tau$$_{f}$ were shown 0 ppm/$^{\circ}C$ near x=0.8.TEX> near x=0.8.0.8.

• Korean Journal of Materials Research
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• v.30 no.7
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• pp.343-349
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• 2020

NKN [(Na,K)NbO₃] is a candidate lead-free piezoelectric material to replace PZT [Pb(Zr,Ti)O₃]. A single crystal has excellent piezoelectric-properties and its properties are dependent of the crystal orientation direction. However, it is hard to fabricate a single crystal with stoichiometrically stable composition due to volatilization of sodium during the growth process. To solve this problem, a solid solution composition is designed (Na,K)NbO₃-Ba(Cu,Nb)O₃ and solid state grain growth is studied for a sizable single crystal. Ceramic powders of (Na,K)NbO₃-M(Cu,Nb)O₃ (M = Ca, Sr, Ba) are synthesized and grain growth behavior is investigated for different temperatures and times. Average normal grain sizes of individual specimens, which are heat-treated at 1,125 ℃ for 10 h, are 6.9, 2.8, and 1.6 ㎛ for M = Ca, Sr, and Ba, respectively. Depending on M, the distortion of NKN structure can be altered. XRD results show that (NKN-CaCuN: shrunken orthorhombic; NKN-SrCuN: orthorhombic; NKN-BaCuN: cubic). For the sample heat-treated at 1,125 ℃ for 10 h, the maximum grain sizes of individual specimens are measured as 40, 5, and 4,000 ㎛ for M = Ca, Sr, and Ba, respectively. This abnormal grain size is related to the partial melting temperature (NKN-CaCuN: 960 ℃; NKN-SrCuN: 971 ℃; NKN-BaCuN: 945 ℃).

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.987-990
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• 1999

본 연구에서는 $BaTiO_3$를 기본 조성으로 하여 PTC 써미스터를 제조하였으며 여기에 첨가제로서 Ca, Mn, Nb의 양을 순차적으로 변화시켜 미세구조 및 전기적 특성을 연구하였다. 또한 복소 임피던스 측정을 통해서 PTC 효과에 미치는 주 저항 성분에 대해서 고찰하였다. Ca 첨가 실험에서는 5[mol%] 첨가된 시편에서 $2.3{\times}10^7[\Omega{\cdot}cm]$의 높은 peak 비저항이 나왔으며 Mn과 Nb에서는 각각 0.1[mol%], 0.2[mol%]에서 $1.5{\times}10^8[\Omega{\cdot}cm]$와 $3.71{\times}10^9[\Omega{\cdot}cm]$의 수치가 측정되었다. 또한 Nb 첨가 실험에서는 첨가량이 증가할수록 결정립의 크기가 조밀해지는 현상을 보였다. PTC 효과에 미치는 주 저항 요소에 대해서 관찰한 복소 임피던스 측정에서는 결정립계 저항 성분이 주가 됨을 확인 하였다.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1885-1887
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• 1999

본 연구에서는 $BaTiO_3$를 기본조성으로하는 반도성 세라믹스인 PTC 써미스터에 $Nb_2O_5$을 미량 첨가하여 미세구조 및 PTCR의 전기적 특성에 대해서 연구하였다. 또한 복소 임피던스 측정을 통하여 $Nb_2O_5$ 첨가에 따른 grain, grain boundary 저항변화에 대해서도 고찰하였다. $(Ba_{0.9}Sr_{0.05}Ca_{0.05})TiO_3-0.01SiO_2-0.001MnCO_3$를 기본조성으로 하여 $Nb_2O_5$ 첨가량을 $0.15{\sim}0.2mol%$까지 변화시켰으며 소결조건은 소결온도 $1350^{\circ}C$, 2h 유지하였으며 냉각속도는 $100^{\circ}C/h$로 하였다 첨가된 Nb의 양이 증가할수록 grain의 크기는 점차로 작아졌으며 상온저항과 peak 저항이 함께 증가하였다. 0.15mol% 첨가된 시편의 경우 상온저항은 $19[\Omega]$이었으며 peak 저항은 $5{\times}10^6[{\Omega}]$정도가 되었다.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.846-849
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• 2003

Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2＋}$, $Pb^{2＋}$,$ Ca^{2＋}$ , $Bi^{3＋}$ , $La^{3＋}$ , $Ti^{4＋}$ , $Mo^{6＋}$ , and $W^{6＋}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2＋}$ , $Ba^{2＋}$ , $La^{3＋}$ doping, but the transition temperature increased with $Ca^{2＋}$ , $Bi^{3＋}$ , $Ti^{4＋}$, $Mo^{6＋}$ , or$ W^{6＋}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

• The Journal of the Petrological Society of Korea
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• v.6 no.1
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• pp.19-33
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• 1997

This study reports the results about the petrography and geochemical characteristics of 10 representative volacanic rocks. The Cretaceous volcanic rocks distributed in the vicinity of the Kageo island composed of andesitic rocks, dacitic welded tuff, and rhyolitic rocks in ascending order. Sedimentary rock is the basement in the study area covered with volcanic rocks. Andesitic rocks composed of pyroclastic volcanic breccia, lithic lapilli tuff and cryptocrystallin lava-flow. Most dacitic rocks are lapilli ash-flow welded tuff. Rhyolitic rocks consists of rhyolite tuff and rhyolite lava flow. Rhyolite tuff are lithic crystal ash-flow tuff and crystal vitric ash-flow tuff with somewhat accidental fragments of andesitic rocks, but dacitic rocks. The variation of major and trace element of the volcanic rocks show that contents of $Al_2O_3$, FeO, CaO, MgO, $TiO_2$ decrease with increasing of $SiO_2$. On the basis of Variation diagrams such as $Al_2O_3$ vs. CaO, Th/Yb vs. Ta/Yb, and $Ce_N/YB_N$ vs. $Ce_N$, these rocks represent mainly differentiation trend of calc-alkaline rock series. On the discriminant diagrams such as Ba/La and La/Th ratio, Rb vs. Y + Nb, the volcanic rocks in study area belongs to high-K Orogenic suites, with abundances of trace element and ternary diagram of K, Na, Ca. According to the tectonic discriminant diagram by Wood, these rocks falls into the diestructructive continental margin. K-Ar ages of whole rocks are from andesite to rhyolite $97.0{\pm}6.8~94.5{\pm}6.6,\68.9{\pm}4.8,\61.5{\pm}4.9~60.7{\pm}4.2$ Ma, repectively. Volcanic rocks in study area show well correlation to the Yucheon Group in terms of rock age dating and geochemcial data, and derived from andesitic calc-alkaline magma that undergone low pressure fractional crystallization dominated plagioclase at <30km.

• The Journal of the Petrological Society of Korea
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• v.27 no.1
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• pp.37-47
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• 2018

Volcanic ash samples of historical eruptions from Mt. Baekdu were analyzed for major oxides, trace and rare earth elements by a variety of analytical techniques. The results indicate that the ashes consist of approximately 58.8~71.1 wt.% $SiO_2$, 9.6~16.8 wt.% $Al_2O_3$, 4.5~6.9 wt.% $Fe_2O_{3t}$, 0.1~1.7 wt.% MgO, 0.3~1.6 wt.% CaO, 5.2~6.3 wt.% $Na_2O$, 4.3~5.9 wt.% $K_2O$ and less than 1.2 wt.% $TiO_2$. Thirty two trace metals including Ba, Cu, Cr. Co, Ni, Sr, V, Zn, and Zr were analyzed. The ashes can be divided two groups: group A(1 ka Millennium pumice, 1668 and $190{\underline{3}}$ pumice) and group B(1702 pumice) according to the relative enrichment of HREEs. The abundances of heavy metals such as Cu, Co, Mn, and Zn were relatively low. As compared to the Sakurajima volcanic ash, Baekdusan volcanic ash has low concentrations of Y, Nb, Pb, U, Sc, V, Ni and Cu and high concentrations of Zr, Ba, Hf, Cr, Co, Zn and rare-earth (except Eu).

• The Journal of the Petrological Society of Korea
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• v.12 no.3
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• pp.119-134
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• 2003

Yuksipryeong two-mica granite presents strongly peraluminous characteristics in both mineralogy and geochemistry. It has high aluminum saturation index with 1.15∼l.20 and high corundum with 2.20∼2.98 wt% CIPW norm. As the color index is <16% and FeO$\^$T/+ MgO + TiO$_2$is average 1.9 wt％, it corresponds to leucogranite. Yuksipryeong two-mica leucogranite shows negative linear trend for TiO$_2$, Al$_2$O$_3$, FeO, Fe$_2$O$_3$, MgO, CaO, K$_2$O, P$_2$O$\_$5/, Rb, Ba, and Sr as SiO$_2$increases, and the positive relation of Zr and Th, which result from feldspar, biotite, apatite and zircon fractionation. Pegmatitic dike has higher SiO$_2$and P$_2$O$\_$5/, but lower another major elements. Yuksipryeong two-mica leucogranite has lower Rb, but higher Ba and Sr than Manaslu, Hercynian two-mica leucogranites, and S-type granites in Lachlan Fold Belt. Pegmatitic dike has higher Rb and Nb but lower Ba, Sr, Zr, Th, and Pb contents than Yuksipryeong two-mica leucogranite, resulting in removing or mobilizing for some trace elements from the granitic melt. Yuksipryeong two-mica leucogranite has total REEs with 95.7∼l23.3 ppm, and chondrite-normalized REE pattern is very steep ((La/Yb)$\_$N/ = 6.9∼24.8), light REEs (LREEs)-enriched End heavy REEs (HREEs)- depleted pattern with low to moderate Eu anomalies (Eu/Eu＊= 0.7∼0.9). While pegmatitic dike has low total REEs with 7.0 ppm, and chondrite-normalized REE pattern is flat-pattern ((La/Yb)$\_$N/ = 2.1) with strong negative Eu anomalies (Eu/Eu＊= 0.2). The melt compositions having formed two-mica leucogranites depend on not only the source rock but also the amounts of the residual remaining after melting of source rocks. The CaO/Na$_2$O and Rb/Sr-Rb/Ba ratios depend mainly on the composition of source rocks in the strongly peraluminous granite, that is, plagioclase/clay ratio of the source rocks. Yuksipryeong two-mica leucogranite has higher CaO/Na$_2$O and lower Rb/Sr-Rb/Ba ratios than Manaslu and Hercynian two-mica leucogranites (Millevaches and Gueret) derived from clay-rich, plagioclase-poor (polite), which suggest that the probable source rocks for Yuksipryeong two-mica leucogranite is clay-poor, plagioclase-rich quartzofeldspathic rocks. As the concentrations of Al$_2$O$_3$remain nearly constant but those of TiO$_2$increases as increasing temperature in the strong peraluminous melt, the Al$_2$O$_3$/TiO$_2$ratio may reflect relative temperature at which the melts have formed. Comparing the polite-derived Manaslu and Hercynian two- mica leucogranites, Manaslu two-mica leucogranite has higher Al$_2$O$_3$/TiO$_2$ratio than latter, and its melt have formed at relatively lower temperature ($\leq$ 875$^{\circ}C$) than Hercynian two-mica leucogranites. Likewise, comparing the quartzofeldspathic rock-derived granites, Yuksipryeong two-mica granite has higher Al$_2$O$_3$/TiO$_2$, ratio than S-type granites in Lachlan Fold Belt (>875$^{\circ}C$). The melt formed Yuksipryeong two-mica leucogranite are considered to have been formed at temperature at below the maximum 875$^{\circ}C$C$.

• Journal of the Korean earth science society
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• v.27 no.1
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• pp.49-60
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• 2006

The purpose of this study is to investigate geochemical characteristics for stream sediments in the Naju area. We collected 139 stream sediments samples from primary channels. Samples were dried slowly in the laboratory and chemical analysis was carried out using XRF. ICP-AES and NAA. In order to investigate geochemical characteristics, the geological groups categorized into granitic gneiss area, schist area, granite area, arenaceous rock area, tuff area, andesite area, and rhyolite area. Average contents of major elements for geological groups are $SiO_2\;58.37{\sim}66.06wt.%,\;Al_2O_3\;13.98{\sim}18.41wt.%,\;Fe_2O_3\;4.09{\sim}6.10wt.%,\;CaO\;0.54{\sim}1.33wt.%,\;MgO\;0.86{\sim}1.34wt.%,\;K_2O\;2.38{\sim}4.01wt.%,\;Na_2O\;0.90{\sim}1.32wt.%,\;TiO_2\;0.82{\sim}1.03wt.%,\;MnO\;0.09{\sim}0.15wt.%,\;P_2O_5\;0.11{\sim}0.18wt.%$. According to the comparison of average contents of major elements, $Al_2O_3\;and\;K_2O$ are higher in granitic gneiss area, $Fe_2O_3,\;CaO,\;P_2O_5$ are higher in tuff area, MgO and $TiO_2$ are higher in andesite area, $Na_2O_$ is higher in rhyolite area, $SiO_2$, and MnO are higher in arenaceous rock area. Average contents of minor and rare earth elements for geological groups are $Ba\;1278{\sim}1469ppm,\;Be\;1.1{\sim}1.5ppm,\;Cu\;18{\sim}25ppm,\;Nb\;25{\sim}37ppm,\;Ni\;16{\sim}25ppm,\;Pb\;21{\sim}28ppm,\;Sr\;83{\sim}155ppm,\;V\;64{\sim}98ppm,\;Zr\;83{\sim}146ppm,\;Li\;32{\sim}45ppm,\;Co\;7.2{\sim}12.7ppm,\;Cr\;37{\sim}76ppm,\;Cs\;4.8{\sim}9.1ppm,\;Hf\;7.5{\sim}25ppm,\;Rb\;88{\sim}178ppm,\;Sc\;7.7{\sim}12.6ppm,\;Zn\;83{\sim}143ppm,\;Pa\;11.3{\sim}37ppm,\;Ce\;69{\sim}206ppm,\;Eu\;1.1{\sim}1.5ppm,\;Yb\;1.8{\sim}4.4ppm$. According to the comparison of average contents of minor and rare earth elements for geological groups, Pb, Li, Cs, Hf, Rb, Sb, Pa, Ce, Eu, and Yb are higher in granitic gneiss area; Ba, Co, and Cr in schist area; Nb, Ni, and Zr in arenaceous rock area; Sr in tuff area: and Be, Cu, V, Sc, and Zn are such in andesite area.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.19-25
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• 2010

Traditional Kr$\ddot{o}$ger-Vink (K-V) notation defines sites in ionic crystals as interstitial or belonging to host ions. It enables description and calculations of combinations of native and foreign defects, including dopants and substituents. However, some materials exhibit inherently disordered partial occupancy of ions and vacancies, or partial occupancy of two types of ions. For instance, the high temperature disordered phases of $Bi_2O_3$, $Ba_2In_2O_5$, $La_2Mo_2O_9$, mayenite $Ca_{12}Al_{14}O_{33}$, AgI, and $CsHSO_4$ are all good ionic conductors and thus obviously contain charged point defects. But traditional K-V notation cannot account for a charge compensating defect in each case, without resorting to terms like "100% substitution" or "Frenkel disorder". the former arbitrary and awkward and the latter inappropriate. Instead, a K-V compatible nomenclature in which the partially occupied site is defined as the perfect site, has been proposed. I here introduce it thoroughly and provide a number of examples.