Thongkam, Montree

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Thongkam, Montree
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montree.th@kmitl.ac.th

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    Electrical and optical properties of p-type CuFe1-xSn xO2 (x = 0.03, 0.05) delafossite-oxide
    (2013-01-14)
    Ruttanapun, Chesta
    ;
    Boonchom, Banjong
    ;
    Thongkam, Montree
    ;
    Kongtaweelert, Samart
    ;
    Thanachayanont, Chanchana
    The CuFe<inf>1-x</inf>Sn<inf>x</inf>O<inf>2</inf> (x = 0.03, 0.05) delafossite samples have been synthesized by a solid-state reaction to investigate electrical and optical properties of the transparent conducting oxide materials. Crystal structure was characterized by XRD. The electrical conductivity and Seebeck coefficient were measured in the high temperature range of 300 to 960 K, while the Hall coefficient, XPS, and UV-VIS-NIR spectra were analyzed at room temperature. The XRD peaks of the samples indicate the delafossite structure phase, and the XPS spectra reveal the stable Sn <sup>2+</sup>-doping state. The Seebeck and Hall coefficient display a positive sign indicating the p-type conducting oxide. The optical allowed direct gap is 3.45 eV as a visible-transparent material. The activation energies for polaron hopping between Sn<sup>2+</sup> sites and Fe<sup>3+</sup> sites of 36 and 32 meV are obtained from the samples having x = 0.03 and 0.05, respectively. The CuFe<inf>1-x</inf>Sn<inf>x</inf>O<inf>2</inf> delafossite oxide compounds, of which the Fe<sup>3+</sup> sites in the CuFeO<inf>2</inf> are substituted by the Sn<sup>2+</sup> ions, are p-type transparent conducting oxide materials. The activation energy is found to decrease with an increased in Sn content. © 2013 American Institute of Physics.
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    A simple route to synthesize new binary cobalt iron cyclotetraphosphate CoFeP4O12 using aqueous and acetone media
    (2009-11-03)
    Boonchom, Banjong
    ;
    Thongkam, Montree
    ;
    Kongtaweelert, Samart
    ;
    Vittayakorn, Naratip
    A new binary cobalt iron cyclotetraphosphate, CoFeP<inf>4</inf>O<inf>12</inf> was synthesized through solid phase reaction using cobalt carbonate, iron metal and phosphoric acid in the presence of water-acetone media with further calcinations at the temperature of 500 °C. The particle size obtained from X-ray line broadening is 65 ± 24 nm for the CoFeP<inf>4</inf>O<inf>12</inf>. FTIR spectrum of CoFeP<inf>4</inf>O<inf>12</inf> is assigned based on the P<inf>4</inf>O<inf>12</inf><sup>4-</sup> ion in the structure. The SEM micrograph of the synthesized CoFeP<inf>4</inf>O<inf>12</inf> shows non-uniform microparticle, which is important for specific application. Room temperature magnetization result shows superparamagnetic behavior of the CoFeP<inf>4</inf>O<inf>12</inf> powder, having no hysteresis loop in the range of ±10,000 Oe with the specific magnetization value of 14.243 emu/g. The XRD and FTIR results of the synthesized CoFeP<inf>4</inf>O<inf>12</inf> appear to be very similar to that of M<inf>2</inf>P<inf>4</inf>O<inf>12</inf> (M = Co and Fe), which indicates the monoclinic phase with space group C2/c. © 2009 Elsevier B.V.
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    Flower-like microparticles and novel superparamagnetic properties of new binary Co1/2Fe1/2(H2PO4) 2·2H2 O obtained by a rapid solid state route at ambient temperature
    (2009-12-01)
    Boonchom, Banjong
    ;
    Thongkam, Montree
    ;
    Kongtaweelert, Samart
    ;
    Vittayakorn, Naratip
    A new binary Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O was synthesized by a simple, rapid and cost-effective method using CoCO<inf>3</inf>-Fe(c)-H<inf>3</inf>PO<inf>4</inf> system at ambient temperature. Thermal treatment of the obtained Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O at 600 °C yielded as a binary cobalt iron cyclotetraphosphate CoFeP<inf>4</inf>O<inf>12</inf>. The FTIR and XRD results of the synthesized Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and its final decomposed product CoFeP<inf>4</inf>O<inf>12</inf> indicate the monoclinic phases with space group P2<inf>1</inf>/n and C2/c, respectively. The particle morphologies of both binary metal compounds appear the flower-like microparticle shapes. Room temperature magnetization results show novel superparamagnetic behaviors of the Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and its final decomposed product CoFeP<inf>4</inf>O<inf>12</inf>, having no hysteresis loops in the range of ±10,000 Oe with the specific magnetization values of 0.045 and 12.502 emu/g at 10 kOe, respectively. The dominant physical properties of the obtained binary metal compounds (Co<inf>1/2</inf>Fe<inf>1/2</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and CoFeP<inf>4</inf>O<inf>12</inf>) are compared with the single compounds (M(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and M<inf>2</inf>P<inf>4</inf>O<inf>12</inf>; where M = Co, Fe), indicating the presence of Co ions in substitution position of Fe ions. © 2009 Elsevier Ltd. All rights reserved.
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