• Title/Summary/Keyword: Rietveld Analysis

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Crystal Structure and Electrochemical Performance of LiNi1-xCoxO2 (x=0.0~1.0) According to Co Substitution (Co 치환량에 따른 LiNi1-xCoxO2 (x=0.0~1.0)의 결정구조 및 전기화학 특성)

  • Hong, Jin K.;Oh, Seung M.
    • Journal of the Korean Electrochemical Society
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    • v.6 no.1
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    • pp.1-5
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    • 2003
  • [ $LiNi_{1-x}Co_xO_2\;(x=0.0\~1.0)$ ] powders were synthesized by citrate method, and their crystal structures and electrochemical performance as the cathode material in Li secondary batteries were analyzed. X-ray diffraction analysis revealed that all the samples carry a single phase regardless of the Co substitution. The results of Rietveld refinement suggested that the crystal structure of solid solutions varies according to the Co substitution. When the Co substitution is low $(x=0.3\~0.5)$, the solid solutions carry a cubic-like structure with a relatively small value in the ratio of lattice parameters (c/a). The solid solutions made with a higher Co substitution (x=0.7), however, exhibit a layered structure with a higher c/a ratio. This difference was also observed in the electrochemical voltage spectroscopy (EVS) profiles, whereby the Co component in scarcely substituted materials shows a charging reaction at $3.7V\;(vs.\;Li/Li^+)$, but in the heavily substituted ones at 3.92V.

Fe-doped beta-tricalcium phosphate; crystal structure and biodegradable behavior with various heating temperature (Fe 이온 치환 beta-tricalcium phosphate의 하소 온도에 따른 미세구조 및 분해 특성)

  • Yoo, Kyung-Hyeon;Kim, Hyeonjin;Sun, Woo Gyeong;Yoon, Seog-Young
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.30 no.6
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    • pp.244-250
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    • 2020
  • β-Tricalcium phosphate (β-TCP, Ca3(PO4)2) is a kind of biodegradable calcium phosphate ceramics with chemical and mineral compositions similar to those of bone. It is a potential candidate for bone repair surgery. To improve the bioactivity and osteoinductivity of β-TCP, various ions doped calcium phosphate have been studied. Among them, Iron is a trace element and its deficiency in the human body causes various problems. In this study, we investigated the effect of Fe ions on the structural variation, degradation behavior of β-TCP. Fe-doped β-TCP powders were synthesized by the coprecipitation method, and the heat treatment temperature was set at 925 and 1100℃. The structural analysis was carried out by Rietveld refinement using the X-ray diffraction results. Fe ions existed in a different state (Fe2+ or Fe3+) with different heat treatment temperatures, and the substitution sites (Ca-(4) and Ca-(5)) also changed with temperature. The degradation rate was fastest at Fe-doped β-TCP with heated at 1100℃. The cell viability behavior was also enhanced with the substitution of Fe ions. Therefore, the substitution of Fe ion has accelerated the degradation of β-TCP and improved the biocompatibility. It could be more utilized in biomedical devices.

Phase evaluation of Fe/Co pigments coated porcelain by rietveld refinement (리트벨트 정밀화법에 의한 Fe/Co 안료가 코팅된 도자기의 상분석)

  • Nam-Heun Kim;Kyung-Nam Kim
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.33 no.5
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    • pp.174-180
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    • 2023
  • Porcelain (white ware, celadon ware) coated with a ferrous sulfate and ferrous/cobalt sulfate was sintered at 1250℃. The specimens were investigated by HR-XRD, FE-SEM, HR-EDS, and UV-vis spectrophotometer. Through X-ray rietveld quantitative analysis, quartz and mullite were found to be the main phases for white ware, and mullite and plagioclase were found to be the main phases for celadon ware. When the pigment of ferrous/cobalt sulfate was applied, were identified as an andradite phase for celadon ware and a spinel phase for the white ware, and the amorphous phase, respectively. The L* value, which was the brightness of the specimen, was 72.01, 60.92 for white ware and celadon ware, respectively. The ferrous and ferrous/cobalt pigment coated porcelain had L* values of 44.89, 52.27 for white ware and celadon ware, respectively; with a* values of 2.12, 1.40, an d at b* values of 1.45 and 13.79. As for the color of the specimens, it was found that the L* value was greatly affected by the white ware, and the b* value differed greatly depending on the clay. It was thought to be closely related to the production of the secondary phase such as Fe2O3 and andradite phase produced in the surface layer.

Synthesis of Tetragonal Barium Titanate Powder by Solvothermal Technique (용매열법에 의한 정방정 티탄산 바륨 분말의 합성)

  • Kwon, Soon-Gyu;Choi, Kyoon;Pee, Jae-Hwan;Choi, Eui-Seok
    • Journal of the Korean Ceramic Society
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    • v.42 no.2 s.273
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    • pp.123-126
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    • 2005
  • Barium Titanate (BT) powders were synthesized by solvothermal method with an ethanol as a solvent. The average particle size was increased with the feedstock concentration: the size was 59 nm at $6.25{\times}10^{-2}$ M and 89 nm at 0.5 M. The sample obtained at 0.5 M concentration was analysed by Rietveld refinement and the mole fraction of tetragonal phase was $75.5\%$ and lattice parameter of tetragonal phase was a=0.3999 (nm), c=0.4032 (nm), and cubic phase was a=0.4015 (nm). TEM analysis for the samples with condition of annealing at $500^{\circ}C$ for I h showed that hydroxyl ions on oxygen sites were not found for these experimental conditions.

Structure Refinement and Equation of State Studies of the Exsoluted Ilmenite-Hematite (티탄철석-적철석 용출시료의 구조분석과 상태방정식 연구)

  • Hwang, Gil-Chan;Kim, Young-Ho
    • Journal of the Mineralogical Society of Korea
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    • v.24 no.3
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    • pp.195-204
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    • 2011
  • Exsolution intergrowth of ilmenite and hematite was studied by the Rietveld refinement method. According to the analysis on these two structural analog minerals, it was found that octahedron (M2) of Ti in ilmenite is in the least deformation, then that (M1) of Fe in ilmenite is deformed next, and octaheron deformation of Fe in hematite is between M1 and M2. High pressure compression experiment was performed up to 5.8 GPa, where two minerals' XRD peaks merged completely. Ilmenite shows normal compression behavior, whereas hematite shrinks in very small amount. This kind of abnormal behavior might be due to the differential response to the applied pressure corresponding to the different compressibilities of the minerals each other.

Crystal Structure and Low Temperature Magnetic Properties of Melt-Spun $Sm_{2}Co_{7}B_{3}$ Compound (급냉응고된 $Sm_{2}Co_{3}B_{7}$ 화합물의 결정구조와 저온 자기특성)

  • Yang, C.J.;Lee, W.Y.;Choi, S.D.
    • Journal of the Korean Magnetics Society
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    • v.3 no.4
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    • pp.284-288
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    • 1993
  • Low temperature magnetic properties and crystal structures of melt-spun $Sm_{2}Co_{7}B_{3}$ compound were characterized. The magnetic measurements in the temperature range 77 K~450 K indicated that a spin-reorientation took place at about 150~160 K. A large anisotropy was observed(Ha=135 kOe at 300 K, 725 kOe at 77 K) for $Sm_{2}Co_{7}B_{3}$ although the magnetic moment is rather low. The crystal structure of the $Sm_{2}Co_{7}B_{3}$ compound was analyzed in detail by Rietveld analysis of powder diffraction pattern, and it was revealed that B(4h) atoms are not placed in the Sm(2e) layer but in between the Sm(2e) and Co($6i_{1}$) layers.

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Effects of Crystallization Behavior on Microwave Dielectric Properties of CaMgSi2O6 Glass-Ceramics

  • Choi, Bo Kyeong;Kim, Eung Soo
    • Journal of the Korean Ceramic Society
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    • v.50 no.1
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    • pp.70-74
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    • 2013
  • Dependence of microwave dielectric properties on the crystallization behaviors of $CaMgSi_2O_6$ (diopside) glass-ceramics was investigated with different heat treatment methods (one and/or two-step). The crystallization behaviors of the specimens, crystallite size and degree of crystallization, were evaluated by differential thermal analysis (DTA), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis by combined Rietveld and reference intensity ratio (RIR) methods. With an increase in heattreatment temperature, the dielectric constant (K) and the quality factor (Qf) increased due to the increase of the crystallite size and degree of crystallization. The specimens heat-treated by the two-step method had a higher degree of crystallization than the specimens heat-treated by the one-step method, which induced improvement in the quality factor (Qf) of the specimens.

Properties of Kaolinite as a Raw Material for Porcelain

  • Kim, Jong-Young;Hwang, Kwang-Taek
    • Journal of the Korean Ceramic Society
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    • v.56 no.6
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    • pp.566-576
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    • 2019
  • In this work, we investigated kaolinite raw materials from China, Vietnam, and Seongju (Korea) used for the manufacture of porcelain products in Korea. According to chemical analysis results, for the kaolinites from Seongju, more feldspar components containing CaO, K2O, and Na2O are found than in those from China or Vietnam, of which the composition is close to that of pure kaolinite. Through X-ray Rietveld quantitative analysis, kaolinite and muscovite are found to be the main phases for all the raw materials. Halloysite, quartz, gibbsite, and andesine are found at more than 5% for KM-85 (China), LKC-60 (Vietnam), KC-009 (China), and WA (Seongju). Absorption rate is on order of LKC-60 < KC-009 < KM-85 < PA < WA, and the sample, sintered in reductive atmosphere, exhibits the lowest absorption rate. Comparing the color of the sintered samples, kaolinites of KM-85, LKC-60, and KC-009 (L*: 94 - 97%) show higher whiteness value than those of WA and PA (L*: 82 - 91%).

A Quantitative Study for Hydrothermal Alteration Zones using Short Wavelength Infrared Spectrometry (단파장적외선 분광분석법을 이용한 열수변질대 정량화 연구)

  • Kim, Yong-Hwi;Choi, Seon-Gyu;Ko, Kwang-Beom;Han, Kyeong-Soo;Koo, Min-Ho
    • Economic and Environmental Geology
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    • v.50 no.1
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    • pp.15-26
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    • 2017
  • Advanced argillic, argillic, and phyllic zones are the most important alteration patterns to predict the hidden ore body during exploration of hydrothermal deposits. We examined the quantitative relationship between the spectral absorption characteristics and the mineral content of the synthetic mixtures such as alunite-kaolinite and illite-kaolinite using short wavelength infrared (SWIR) spectroscopy. In the alunite-kaolinite mixtures, the spectral absorption characteristics of the alunite was highly correlated with the Hull quotient reflectance(0.99) and the kaolinite had the highest correlation with the Gaussian peak(0.92). Illite-kaolinite mixtures are essential for Gaussian deconvolution because of the overlap of absorption region. Illite and kaolinite mixtures indicate the high correlation of 0.93 and 0.98, respectively. The error ranges in the alunite-kaolinite(8%) and illite-kaolinite mixtures(5%) derived from SWIR were smaller than the ones(29% and 26%) obtained from X-ray diffraction(Rietveld) analysis. These results show that SWIR spectroscopic analysis is more reliable than XRD Rietveld analysis in terms of quantification of allowed minerals.

Structural and electrical properties of lead free ceramic: Ba(Nd1/2Nb1/2)O3

  • Nath, K. Amar;Prasad, K.;Chandra, K.P.;Kulkarni, A.R.
    • Advances in materials Research
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    • v.2 no.2
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    • pp.119-131
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    • 2013
  • Impedance and electrical conduction studies of $Ba(Nd_{1/2}Nb_{1/2})O_3$ ceramic prepared using conventional high temperature solid-state reaction technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group $Pm\bar{3}m$. Energy dispersive X-ray analysis and scanning electron microscopy studies were carried to study the quality and purity of compound. The circuit model fittings were carried out using the impedance data to find the correlation between the response of real system and idealized model electrical circuit. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in $Ba(Nd_{1/2}Nb_{1/2})O_3$. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy.