• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.244-252
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• 1997

The pseudo-spinel type solid solution, $LiAl_{2.5}/Fe_{2.5}O_8$ was prepared by reaction of $LiCO_3, Al_2O_3, Fe_2O_3$ mixture at 1620K, which can be used for cathode material in lithium batteries. Its structure was investigated by Rietveld profile-analysis of XRD in detail. The space group of solid solution is $P4_3$32(a=8.1293$\AA$) and the final residual index of structure refinement was about 5%. Cations $Al^{3+}, Fe^{3+}$ are located at both tetra- and octahedral-coordination and $Li^+$ ions are occupied in the octahedral 4b-, 12d-site of the inverse spinel.

• Progress in Superconductivity
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• v.1 no.2
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• pp.135-140
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• 2000

Distribution of Pr ions between Y- and Ba-site of the $Y(Ba_{1-Xn}Pr_{Xn})_2Cu_3O_y$ ($0{\leq}Xn{\leq}{0.3}$, Xn : nominal composition) material prepared by the solid state reaction method was studied. Although the samples have narrow superconducting transition, tiny peaks of $Y_2BaCuO_5$ impurity phase are included in the x-ray diffraction patterns suggesting that some of the Pr ions are entered into the Y-site. The distribution of Pr ions between Y- and Ba-site was determined by measuring the mass fraction of YBCO and $Y_2BaCuO_5$ phase for each sample through the Rietveld analysis of the x-ray diffraction data. About 60 % of Pr ions occupy the Y-site regardless of the Pr content. Various superconducting parameters such as the oxygen content and the hole concentration etc. are compared before and after the impurity correction.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.11-18
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• 2020

Carbon nanotubes are used in various industries with their excellent mechanical properties and electrical conductivity. In the construction industry, research is being conducted to give self-sensing capabilities to structures, but the results of experiments vary among researchers, and the analysis is insufficient. Therefore, in this study, the hydration and electrical properties of MWCNT-added cement pastes were measured. The electrical resistance values of hydration heat, porosity, Rietveld quantitative analysis, compressive strength, and distance were measured.. The heat resistance, porosity, Rietvelt quantitative analysis, compressive strength and distance were measured according to electrical resistance. Experimental results showed that the heat of hydration decreased with increasing MWCNT. XRD Rietveld quantitative analysis showed that there was no significant difference in the amount of hydration products with increasing addition rate of MWCNT. As a result of SEM analysis, the MWCNT is agglomerated by van der Waals forces, and this area is considered to be caused by voids and weak areas. The electrical resistance value decreases as the addition rate is increased, and thus may play a role for magnetic sensing in the future.

• Journal of the Mineralogical Society of Korea
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• v.26 no.1
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• pp.27-34
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• 2013

X-ray powder diffraction is one of the most powerful techniques for qualitative and quantitative analysis of crystalline compounds. Thus, there exist a number of different methods for quantifying mineral mixtures using X-ray diffraction pattern. We present here the use of Rietveld and PONKCS (partial or no known crystal structure) methods for quantification of amorphous and crystallized mineral phases in synthetic mixtures of standard minerals (amorphous silica, quartz, mullite and corundum). Pawley phase model of amorphous silica was successfully built from the pattern of 100 wt% amorphous silica and internal standard-spiked samples by PONKCS approach. The average of absolute bias for quantities of amorphous silica was 1.85 wt%. The larger bias observed for lower quantities of amorphous silica is probably explained by low intensities of diffraction pattern. Averages of absolute bias for minerals were 0.53 wt% for quartz, 0.87 wt% for mullite and 0.57 wt% for corundum, respectively. The PONKCS approach achieved improved quantitative results compared with classical Rietveld method by using an internal standard.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.1-6
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• 1996

A single phase Ba2(Ti8,472Zr0.528)O20 was prepared by the oxalate method from aqueous solution of BaCl2 TiCl4 and ZrOCl2. The structure ananlysis has been carried out by Rietveld analysis method at room temperature. Powder X-ray data of Ba2(Ti8,472Zr0.528)O20 was indexed with the triclinic lattice(a=7.4587 $\AA$ b=14.0672 $\AA$, c=13.3327 $\AA$, $\alpha$=89.87, $\beta$=79.45 ${\gamma}$=84.46) The R (Residual) values of structure refinement were in a range between 10.00 and 8.00 This analysis proved that the added Zr occupied Ti sites in th structure of Ba2Ti9O20. Ba2(Ti8,472Zr0.528)O20 has excellent dielectric properties(dielectric constant K=40.49 at 5.42 GHz Q=4621) so that it can be used as good microwave dielectric materials.

• The Korean Journal of Ceramics
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• v.6 no.4
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• pp.380-384
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• 2000

Crystal structure of $Ba_5-5X$Y$_10/3$Nb$_10$O$_30$ was tried to determine by Rietveld analysis using powder X-ray diffraction data. This compound has tetragonal tungsten bronze (TTB) structure with general formula, (Al)$_2$(A2)$_4$(B1)$_2$(B2)$_8$(O1)$_8$(O2)$_8$(O3)$_4$(O4)$_2$(O5)$_4$(O6)$_4$. However, it was difficult to determine the distribution of Ba and Y in Al and A2 sites by the analysis only. Combination of Rietveld analysis and site potentials calculation as well as lattice energy calculations helped to determine the distribution. As the result, it was clarified that $Ba^2+$ cations occupy A2 (pentagonal tunnel site) and $Y^3+$ cations occupy Al (cubic site). The distribution of cations at each site coincides with the distribution estimated by the difference of ionic radii. This supports the formation condition of TTB which was proposed in our previous report. $Ba_5-5X$Y$_10X/3$Nb$_10$O$_30$ shows ferroelectric characteristics. In this compound, remanent polarization decreases slightly with the composition X. On the other hand, the result of crystal structure determination reveals that atomic positions along c-axis for A1, A2, B1 and B2 cations are also decreased with the composition X. This would suggest that the dependence of remanent polarization on composition X is derived by the dependence of atomic coordinates on composition X.

• Korean Institute of Interior Design Journal
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• no.9
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• pp.49-56
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• 1996

This study is to present the design methods in the Schrider House executed by the Dutch architect G. Th, Rieveld. The plastic principles which underlies the architecture design are examined through the analysis of the 'new structural joint system (Cartesian Coordinate System) ' and ' Color-Plasticity ' which characterized a series of his furniture design from 1918 to 1924. It indicates that Reitveld attempted to realize the simplicity, clarity and flexibility of spatial expression in his first independent architecture by the application of technical skills which have been developed in his early days.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.748-753
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• 1995

Solid solution of NaNb $O_3$70 mol% and SrTi $O_3$30 mol% was single phase. A broad dielectric peak was found at about l00K. Crystal structure was analysed at room temperature and 12K using Rietveld analysis. The unit cell was assigned to have a a doubled lattice parameter of simple perovskite sturcture at room temperatue, the structure was orthorombic with space group Pmmn. At 12K, the structure was also orthorombic with space group Pnma. This structure change with temperature was due to the distortion of oxygen octahedron. This distortion of oxygen octahedron was made by the decrease of (Ti, Nb)-O bounds length with no variation of (Ti, Nb)-O-(Ti, Nb) bound angle. Therefore the broad dielectirc peak about l00K was attributed to the structural change casued by oxygen octahedron distortion.

• Journal of Electrochemical Science and Technology
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• v.4 no.3
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.

• Journal of the Mineralogical Society of Korea
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• v.13 no.3
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• pp.164-170
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• 2000

Neutron single crystal and powder diffraction techniques have been applied to the structure analysis of yttria-stabilized zirconium, Z $r_{0.73}$ $Y_{0.27}$ $O_{1.87}$., prepared by the skull-melting method. The crystal structure has been determined to be cubic symmetry, space group Fm/equation omitted/ with a=5.155(2)$\AA$, V=136.99(5)$\AA$, Z=4, and R(F)=5.65%, $\omega$R(I)=10.57% for 70 integrated intensities of Bragg Peaks observed from single crystal of Z $r_{0.73}$ $Y_{0.27}$ $O_{1.87}$. The stabilizer atoms randomly occupy the zirconium sites and there are displacements of oxygen atoms with amplitudes of $\Delta$/a~0.033 and 0.11 along <110> and <100> directions from the ideal positions of the fluorite structure, respectively. There are no significant differences in crystallographic data between the single crystal and powder studies. Diffraction pattern after Rietveld refinement, using neutron powder data, has shown the evidence of a tetragonal impurity phase, or a slight tetragonal distortion.