• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.293-301
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• 1984

-ray fluorescence analysis of $Ta_2O_5$, $Nb_2O_5$ and $ZrO_2$ in tin-slag samples using the simple dilution method was studied. The method is to correct mathematically the calibration curve to the linear line by the dilution. One synthesized standard having similar composition to the sample and tin slag samples were diluted with anhydrous $Li_2B_4O_7$ at the level of 1%, 2% and 3% of the sample content respectively. The diluted samples were fused at $1150^{\circ}C$ for 30 minutes and these glass beads were finely ground and pelletized. Measuring the X-ray intensities with these pellets, analytical results were calculated by the equation derived from J. Scherman's equation for the characteristic X-ray intensity of an element. Analytical results agreed with the reference values obtained by the standard calibration method within allowable error range and were reproducible.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.302-308
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• 1984

X-ray spectrometric determination of $Ta_2O_54, $Nb_2O_5$ and $ZrO_2$ in tin-slag samples using the double dilution technique was conducted. Tin-slag samples and one synthesized standard sample having similar composition to the samples were diluted with anhydrous $Li_2B_4O_7$ at the level of 1.00, 2.00 and 3.00% of the sample content, respectively. The diluted samples were fused at $1,150^{\circ}C$ for 30 minutes, and these glass beads were finely ground and pelletized. With the X-ray intensities measured, analytical results were calculated by the double dilution equation. The results agreed to the reference values obtained by the standard calibration method and the simple dilution technique within allowable error range and were reproducible.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.221-224
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• 2000

The microwave dielectric properties of Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BMT-BCN] ceramics were investigated. The specimens were prepared by the conventional mixed oxide method. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$ and Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$ formed a solid solution with complex perovskite structure. Increasing the BCN content, dielectric constant was increased, but temperature coefficient of resonant frequency was decreased. In the range of x$\geq$0.4, dielectric constant was about 30. 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $\varepsilon$$_{r}$=30.84, Q$\times$f$_{0}$=75,325[GHz] and $\tau$$_{f}$=-2.9015[ppm/$^{\circ}C$].X>].

• Journal of Powder Materials
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• v.29 no.2
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• pp.110-117
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• 2022

The grain growth behavior in the (1-x)K_0.5Na_0.5NbO₃-xCaZrO₃ (KNNCZ-x) system is studied as a function of the amount of CZ and grain shape. The (1-x)K_0.5Na_0.5NbO₃-xCaZrO₃ (KNNCZ-x) powders are synthesized using a conventional solid-state reaction method. A single orthorhombic phase is observed at x = 0 - 0.03. However, rhombohedral and orthorhombic phases are observed at x = 0.05. The grain growth behavior changes from abnormal grain growth to the suppression of grain growth as the amount of CaZrO₃ (CZ) increases. With increasing CZ content, grains become more faceted, and the step-free energy increases. Therefore, the critical growth driving force increases. The grain size distribution broadens with increasing sintering time in KNNCZ-0.05. As a result, some large grains with a driving force larger than the critical driving force for growth exhibit abnormal grain growth behavior during sintering. Therefore, CZ changes the grain growth behavior and microstructure of KNN. Grain growth at the faceted interface of the KNNCZ system occurs via two-dimensional nucleation and growth.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.795-800
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• 2003

The dielectric and piezoelectric properties of the xPb(A $l_{0.5}$N $b_{0.5}$) $O_3$-(1-x)Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_3$ [xPAN-(1-x)PZT] thin films by pulsed laser deposition (PLD) were investigated as a function of PAN contents. The effect of texture on dielectric and piezoelectric properties of the 0.05PAN-0.95PZT thin films having the highest piezoelectric constant( $d_{33}$) was studied more precisely. For 0$\leq$x$\leq$0.15 compositions in xPAN-(1-x)PZT thin films, the well-developed perovskite phase with (111) preferred orientation was obtained at the deposition temperature of 50$0^{\circ}C$. With increasing PAN content, remanent polarization and coercive field decreased. The dielectric constant increased with an increase of PAN content until it reached 1450 at $\chi$= 0.05, and then decreased for higher PAN content. The maximum points of dielectric constant coincides with the maximum points of the piezoelectric constant $d_{33}$.33/.33/././.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.563-567
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• 2011

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of $0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$ mol% $ZrO_2$ [KNN-SZ+$xZrO_2$; x= 0~0.10] doped with 0.1 wt% $MnO_2$ by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%$H_2-97%N_2$ atmosphere at $1,140^{\circ}C$ exhibit pure perovskite structure irrespective of the content of $ZrO_2$. Meanwhile, the sintering denisty and piezoelectric properties such as $K_p$, $Q_m$ and $d_{33}$ of KNN-SZ samples as a function of $ZrO_2$ content show the maxima ($k_p$=28.07%, $Q_m$= 101.34, $d_{33}$= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+$xZrO_2$ composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.157-168
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• 2005

Trachytic rocks among the bimodal metavolcanic rocks of the Gyemyeongsan Formation and adjacent areas are investigated. Some rocks reveal very high content of iron and most rocks show very high abundances of rare earth elements and high field strength elements. Most rocks show significant Eu negative anomaly, which can be interpreted as the result of plagioclase fractionation. Lack of noticeable Nb negative anomaly indicates not-involvement of crustal material in their generation, which excludes the arc environment or remelting of continental crust from their genetic process. Metatrachytes of the Gymyeongsan Formation are plotted within the within-plate environment of the tectonic discrimination diagram utilizing immobile high field strength element Nb and Y. They also show typical characteristics of A-type magma, such as high Ga content. Considering their affinity to Al-type of Eby (1992) and their age of 750 Ma (Lee et al., 1998), they seem to have been produced by the differentiation of mantle-derived within-plate magmatism at the rift, related with the separation of Neoproterozoic supercontinent Rodinia. Possible connection of Gyemyeongsan and Munjuri Formations of the Okcheon metamorphic belt, at least part of them, to the Cathaysia block of South China during the Neoproterozoic is strongly suggested.

• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.255-259
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• 1999

The effects of $SiO_2$ and MnO addition on the sinterability and the electrical properties of 0.4mol% Nb-doped SrTiO3 varistor were investigated. The $SiO_2$ content was fixed at 0.3mol% and the MnO content varied from 0 to 1.0mol%. With 0.3 mol% $SiO_2$ and 0.3 mol% MnO addition, optimum density was obtained by sintering at $1200^{\circ}C$ without excess liquid phase. Impedance spectroscopy was performed on the sintered specimens with 0.3 mol% $SiO_2$ and various MnO contents. It was found that the resistivities of grains was increased with increasing MnO content. The dielectric constant was measured to be above 50000 in the specimen with 0.3~1.0mol% Mn content. The non-linear coefficient increased substantially with MnO addition, and it varied from 1 to 9 depending on the MnO content.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.263-263
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.98.2-98
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• 2003