• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.31-36
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• 1993

Na-Fe Tourmalene ($NaFe_3Al_6B_3Si_6O_{27}F_4$)single crystals were grown by FZ method. The Growth conditions are counter rotation 20~30rpm, growth rate 1~5mm/hr in the atmospheric environment. The transition elements as Fe(in this research), Mn, Co, etc, are exist in the theoretical fomulae so that dopants were not added. The feed rod was sintered between $1000^{\circ}C$ and $1l00^{\circ}C$, but at higher temperature, it was difficult to manufacture the feed rod because of evaporation of the elements such as F. As grown crystals had a black color and the length of 50~60mm, the diameter of 5~6mm. X-ray powder diffraction pattern indicated that the composition of the feed rod was right to the Tourmaline composition. By FT-IR spectra, the state of bonding of each element was charaterized.

• Journal of the Korean Ceramic Society
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• v.13 no.3
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• pp.13-20
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• 1976

The magnetic properties, especially the magnetostriction, of ferroxplana $Zn_{1-x}$$M_X$Y(x=0.0, 0.2, 0.4, 0.6) were investigated at room temperature. In general, the Curie temperature and the permeability of ferroxplana $Zn_{1-X}$$Mn_X$Y increased while the amount of the other phase decrease with increased concentration of dopant $Mn^{2+} for $Zn^{2+}. The magnetostriction constnats K1, K2, K3 and K4 for ZnY were ＋0.3, -5.0, -4.3 and $-4.8{\times}$$10^{-6} while that for 4Zn^0.8$ $Mn^0.2$Y were ＋2.5, -5.4, -6.0 and $-3.4{\times}10^{-6}$, respectively.

• Bulletin of the Korean Chemical Society
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• v.20 no.6
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• pp.701-704
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• 1999

Metallophthalocyanines [PcM, Pc: phthalocyanine, M: Fe 2+ , Co 2+ ] were reacted with α-isocyanonaphthalene( α-in) and α-isocyanoanthracene (α-ia) to form monomeric complexes. The synthesis and coordination behaviour of the isocyanides as a ligand (L) are discussed. All the products were characterized by spectroscopic methods and instrumental analysis. The electrical conductivities of these complexes, which were not treated with dopant, were attributed to the metal-ligand electron delocalization in the PcML2 complexes. The complexes have an enlarged macrocycle where the π-electron back donating ability of PcM is stronger than the σ-electron coordinating ability of the isonitrile ligands. Their electrical conductivities were measured as σRT = 2.1×10 -9 ~3×10 -10 S/cm. Also thermal stability was investigated in this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.336-336
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• 2013

Zinc oxide (ZnO) based transparent oxide semiconductors have been studied due to their high transmittance and electrical conductivity. Pure ZnO have unstable optical and electrical properties at high temperatures but doped ZnO thin films can have stable optical and electrical properties. In this paper, transparent oxide semiconductors of Y-doped ZnO thin films prepared by sol-gel method. The ionic radius of $Y^{3+}$ (0.90 A) is close to that of $Zn^{2+}$ (0.74 A), which makes Y suitable dopant for ZnO thin films. The Sn-doped ZnO thin films were deposited onto quartz substrates with different atomic percentages of dopant which were Y/Zn = 0, 1, 2, 3, 4, and 5 at.%. These thin films were pre-heated at $150^{\circ}C$ for 10 min and then annealed at $500^{\circ}C$ or 1 h. The structural and optical properties of the Y-doped ZnO thin films were investigated using field-emission scanning electronmicroscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectroscopy, and photoluminescence (PL).

• Progress in Superconductivity and Cryogenics
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• v.17 no.4
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• pp.30-33
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• 2015

We report the synthesis of Ni-doped $BaFe_2Se_3$ single crystals by using a flux method. X-ray diffraction (XRD) of $Ba(Fe_{1-x}Ni_x)_2Se_3$ shows a gradual peak shift with an increase in the nominal Ni-doping rate, x = 0, 0.05, and 0.10, due to a decrease in unit-cell volume. All samples show a spin glass transition, and temperature dependence of magnetic susceptibility shows a negligible change in the spin-glass transition temperature ($T_g$) with Ni concentration x. The temperature dependence of electrical resistivity for $BaFe_2Se_3$ shows an insulating behavior, and the resistivity value at 295 K and the activation energy ($E_a$) obtained from the Arrhenius plot decrease with increasing x. These results suggest that the Ni doping can be effectively worked as a dopant for electron charge carriers, but is less efficient in controlling the magnetic property, such as spin glass transition, in the $BaFe_2Se_3$ compound.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.647-651
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• 2006

A new class of compounds in the form of skutterudite structure, Fe doped $CoSb_3$ with a nominal composition of $Fe_xCo_{4-x}Sb_{12}$ ($0{\leq}x{\leq}2.5$), were synthesized by mechanical alloying of elemental powders followed by vacuum hot pressing. Nanostructured, single-phase skutterudites were successfully produced by vacuum hot pressing using as-milled powders without subsequent heat-treatments for the compositions of $x{\leq}1.5$. However, second phase was found to form in case of $x{\geq}2$, suggesting the solubility limit of Fe with Co in this system. Thermoelectric properties including thermal conductivity from 300 to 600 K were measured and discussed. Lattice thermal conductivity was greatly reduced by introducing a dopant up to x=1.5 as well as by increasing phonon scattering in nanostructured skutterudite, leading to enhancement in the thermoelectric figure of merit. The maximum figure of merit was found to be 0.32 at 600 K in the composition of $Fe_xCo_{4-x}Sb_{12}$.

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.222-231
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• 2001

The material properties of $SnO_2$ were investigated as a function of the amount of $Fe_2O_3$, the partial pressure of oxygen, the concentration of CO gas, and temperature. $Fe_2O_3$-doped $SnO_2$ thick films were prepared by the screen printing technique on alumina substrate. The specimens sintered at $700^{\circ}C$ for 6 hours showed little difference of the grain size and narrow distribution with the content of $Fe_2O_3$. The electrical conductance of undoped $SnO_2$ is high at low firing temperature and at low partial pressure of oxygen. The electrical conductance of $Fe_2O_3-$-doped $SnO_2$ is increased with measurement temperature, but decreased with the content of $Fe_2O_3$. The dependence of oxygen partial pressure is decreased with dopant addition. The highest sensitivity and the good properties of response speed and repeatability for CO gas were observed on the specimen with 0.1 mol% $Fe_2O_3$ at $350^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.457-460
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• 2010

$SmCoO_3$ system was investigated for their application to themoelectric materials. All specimens showed p-type semiconducting behavior and their electrical conductivity ($\sigma$), Seebeck coefficient (S) and power factor were measured at high temperature. And the effect of dopant ions on their thermoelectrical properties were also investigated. $Fe^{3+}$ ion doped into $Co^{3+}$ site enhanced the Seebeck coefficient and decreased the electrical conductivity simultaneously. The maximum Seebeck coefficient value for 60% doping case reached to 780 ${\mu}V$/K at $240^{\circ}C$. However $Fe^{3+}$ doped system cause an negative effect on power factor value. In case of the pure phase, the maximum Seebeck coefficient value reached to 290 ${\mu}V$/K at $240^{\circ}C$ and the maximum electrical conductivity was obtained 748 1/(ohm$\times$cm) at $960^{\circ}C$. As a result, the maximum power factor was obtained $1.49\times10^{-4}$ W/$mK^2$ at $550^{\circ}C$.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.393-400
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• 1996

The conducting polymer composites were prepared by imbibing the porous particle with an $FeCl_3$ oxidant solution, drying the imbibed porous particle, and imbibing again with pyrrole solution for polymerization to take place in the pore. The conductivity of the porous composite particles, was higher than that of nonporous particles. Also, the conductivity of composite was increased with increasing specific surface area and pore specific volume of the host porous particles since the degree of formation of conducting polymer in the pore increased.

• Korean Journal of Crystallography
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• v.2 no.1
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• pp.23-26
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• 1991

Amethysts were grown hydrothemally. The origin of amethyst color is iron center, which is developed by correlation between Fe3+(substitutional) and Fe3+ (interstitial)1). Crackless amethysts without smoky centers were grown only from major (1011) and minor (1101) seeds on K2c03 solutions. The violet color of amethyst depended on both iron concentration and amount of irradiation of r-ray. Increasing the iron concentration resulted in the deep violet color. Also amethysts color were changed to dark proportional to amount of irradiation. From visible spectra it was found that increasing the amount of irradiation affected not the character of individual iron center but the total number of iron centers.