• Resources Recycling
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• v.26 no.5
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• pp.61-66
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• 2017

Vanadium Dioxide has been investigated for use as a "spectrally-selective" window coating to block infrared transmission and reduce the loss of building interior heat through windows. The preparation of thermochromic $VO_2$ powder by the reductive reaction with hydrogen was studied. The reductive reaction method has many advantages of easy and mass production of $VO_2$ powder according to controlled reaction without semi-conductor equipments like sputter and beam evaporator. The reaction temperature, time, concentration of reductive gas, post-annealing condition and W addition as dopant would affect the characterization of $VO_2$ powder and its thermochromism. Many applications for electrical device and energy-saving technologies is expected.

• Advances in materials Research
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• v.5 no.2
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• pp.93-105
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• 2016

KNN-based ceramics modified with small amounts of $Bi_4Zr_3O_{12}$ (BiZ) has been synthesized using high-throughput experimentation (HTE). The results from X-ray diffraction show that for samples with base composition $(K_{0.5}Na_{0.5})NbO_3$ (KNN), the phase present changes from orthorhombic to pseudo-cubic with more than 0.2 mol% BiZ addition; for samples with base composition $(K_{0.48}Na_{0.48}Li_{0.04})(Nb_{0.9}Ta_{0.1})O_3$ (KNNLT), the phase present changes from a mixture of orthorhombic and tetragonal symmetry to pseudo-cubic with more than 0.4 mol % while for samples with base composition $(K_{0.48}Na_{0.48}Li_{0.04})(Nb_{0.86}Ta_{0.1}Sb_{0.04})O_3$ (KNNLST), the phase present is tetragonal with <0.3 mol% BiZ addition and transforms to pseudo-cubic with more dopant addition. The microstructures of the samples show that addition of BiZ decreases the average grain size and increases the volume of pores at the grain boundaries. The values of dielectric constant for KNN and KNNLT compositions increase slightly with BiZ addition while that for KNNLST decreases gradually with BiZ addition. The dielectric loss values are between 0.02 and 0.04 for KNNLT and KNNLST compositions while they are ~ 0.05 for KNN samples. The resistivity values increases with BiZ addition and values in the range of $10^{10}{\Omega}cm$ and $10^{12}{\Omega}cm$ are obtained. The piezoelectric charge coefficient ($d{^*}_{33}$) is highest for KNNLST samples and decreases gradually from ~400 pm/V to ~100 pm/V with BiZ addition.

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.40-49
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• 1997

$Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ thermoelectric matcrials havc 11et:n fahricxted hy mechanical alloying and hot pressing methods. Microstructure and thermoelectric properties of the hot 11resseii $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ have been investigated Lvith variations of hot pressing temperature and dopmt atltiition Formation of $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ alloy powders was completed by mechanical alloying of the as-mixed Ri. Te, arid Sc grmules of ~3.6mm size for 3 hours at ball-to-material weight ratio of 5 : 1. Figure of merit of $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ was markedly incrcwieti hy hot pressing at temperatures above $450^{\circ}C$, and value of $1.9{\times}10^{-3}/K$ was obtained for the specimen hot pressed at $550^{\circ}C$. With addition of 0.015 wt% Ri as acceptor dopant, figure of merit ol $Bi_{2}(Te_{0.9}Se_{0.1})_{3}$ hot pressed $550^{\circ}C$$2.1{\times}10^{-3}/K$.

• Clean Technology
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• v.14 no.3
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• pp.171-175
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• 2008

The effect of the addition of $Al^{3+}$ dopant on the electrochemical characteristics of $Li_{4}Ti_{5}O_{12}$ was investigated. $Li_{4}Ti_{5}O_{12}$ is known as a 2ero-strain material, and $Li_{3.95}Al_{0.15}Ti_{4.9}O_{12}$ has been manufactured by solid-state reaction with high energy ball milling (HEBM). The samples were heated at 800, 900 and $1000^{\circ}C$ in electric furnace. The structural and surface structures were measured by XRD (X-ray diffraction) and SEM (scanning electron microscopy). Cut-off voltage of charge/discharge cycles was $1.0{\sim}3.0 V$ to investigate reversible capacity, cycle stability and plateau voltage. The reversible capacity of $Li_{3.95}Al_{0.15}Ti_{4.9}O_{12}$ was 138 mAh/g.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.27-32
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• 2001

The effect of $V_2O_5$, a donor-type dopant on the degradation of quality factor of ($Zr_{0.8}, Sn_{0.2})TiO_4$was compared with Ta$_2$O$_{5}$ doped ($Zr_{0.8}, Sn_{0.2})TiO_4$ in terms of microstructure, electrical conductivity, and oxidation state of the dopant. It is well known that the addition of the donor type species such as $Ta_2O_5,Nb_2O_5, Sb_2O_5, WO_{3}$, increases the quality factor of ($Zr_{0.8}, Sn_{0.2})TiO_4$due to decrease the oxygen vacancy concentration. Unlike other dopants, however, the addition of $V_2O_5$ decreased the quality factor. The degradation of quality factor of ($Zr_{0.8}, Sn_{0.2})TiO_4$was resulted from the formation of grain boundary phase and $V_2O_5$rich fiber shaped secondary phase, and the increasing the oxygen vacancy concentration due to unstability of oxidation state of vanadium ions in ($Zr_{0.8}, Sn_{0.2})TiO_4$ceramic.c.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.336-338
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• 1991

Effects of $Nb_2O_5$ addition ranged from 0.0 to 0.75(wt%) on the microstructure and electrical porperties of PZT ceramics have been investigated. The Pb vacancy concentration increases with increasing NbO content. However, the experimental results show the resistivity increases with increasing $Nb^{5+}$ content. This behavior can be explained as a compensation effect and $Nb^{5+}$ can serve as a donar and contribute electrons to the conduction process. According to the law of mass action, this result may reduce the total charge carrier:thus the resistivity increase with NbO content in PZT.

• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.238-241
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• 1996

New porous BaTiO$_3$ thermistors were fabricated using graphite powders (0 to 10 wt. %) and their porosities were in the range of 9.1% to 16.2%. As results of impedance analysis, it was confirmed that the pores affected the grain-boundary resistance and the bulk (grain interior) resistance was constant as about 25 $\Omega$ at room temperature. The magnitude of PTCR effect $(p_{max}/p)$ markedly increased from 3 orders to 7 orders without addition of any acceptor dopant such as Mn or Cr.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1440-1441
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• 2011

Apatite-lanthanum silicate has attracted considerable interest in recent years due to its high oxide ion conductivity, In this paper, Bi-doped samples $La_8Bi_2(SiO_4)_6O_3$ were prepared by conventional solid-state method and the influences of Bi-dopant content on calcining temperature were reported. The Samples were characterized by X-ray diffraction (XRD) and scanning electron micrograph (SEM) and impedance analysis.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1378-1386
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• 1994

The characteristic of calcined BaTiO3 powder and sintered PTC ceramics was investigated varing with calcination temperature and time of BaTiO(C2O4)2.4H2O synthesized from BaCl2.2H2O, TiCl4, oxalic acid and ethanol by oxalic acid method. When the particle size was less than 0.1 ${\mu}{\textrm}{m}$ by controlling calcination temperature and time, the resistance at room temperature was measured very high (above M{{{{ OMEGA }}). However, when the calcined particle sizes ranged from 0.2 to 0.3 ${\mu}{\textrm}{m}$, the resistance was 100 {{{{ OMEGA }} (After sintering, the grain size was 10~30 ${\mu}{\textrm}{m}$ homogeneously with the addition of dopant in sintering, the resistivity, resistance, $\alpha$ value and jumped to were 110{{{{ OMEGA }}.cm, 24$^{\circ}C$/% and 106{{{{ OMEGA }}, respectively.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.321-335
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• 1999

Erbium(Er) doped LiNbO3(Er:LiNbO3) single crystal gibers were grown free of cracks along the c-axis by micro-pulling down method. the Er3+ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980 nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570 nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of Er2O3 dopant in as-grown Er:LiNbO3 crystals.