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P-Type optoelectronic and transparent conducting oxide properties of delafossite CuAl1/2Fe1/2O2
(2015-12-03)
Ruttanapun, Chesta
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Jindajitawat, Phumin
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Buranasiri, Prathan
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Harnwunggmoung, Adul
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Charoenphakdee, Anek
CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> delafossite was prepared using a solid-state reaction method to investigate its optical and electronic transport properties. CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> formed a hexagonal delafossite structure with an R3¯m space group. The positive Seebeck coefficient and the direct optical gap of 3.6 eV confirmed that the CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> delafossite in a p-type transparent conducting oxide. The fluorescence emission at 390 nm (green emission) confirmed that CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> has a direct transition band gap. Thermogravimetric analysis indicated a weight loss of 1.2%, caused by the intercalation of O atoms, which produced hole carriers from the different ionic radii at the B sites. The electric conductivity at room temperature was thermally activated, as predicted by the small-polaron hopping mechanism, with an activation energy of 75 meV and a charge transport energy of 61 meV. CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> delafossite exhibited p-type optoelectronic behavior and is a transparent conducting oxide, which may be crucial in the p-type photonic and electrode industries.
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Effect of Strong Correlation of Mg2+-doped into Cr3+ Sites of CuCrO2 on Thermoelectric Properties
(2015-09-02)
Ruttanapun, Chesta
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Charoenphakdee, Anek
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Nisoa, Mudtorlep
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Muthitamongkol, Pennapa
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Thanachayanont, Chanchana
This study aims to investigate the strong correlation effect of spin and charge carriers for the Mg2+-substituted into Cr3+ sites of CuCrO2 delafossite on thermoelectric properties. The CuCr0.98Mg0.02O2 sample was synthesized by a solid state reaction. The starting powder CuO, Cr2O3 and MgO were ball milled with poly vinyl alcohol solution for 24 h. The ball milled powder was pressed and sintered in air atmosphere at temperature 1050 C for 6 h. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured at high temperature. The XRD displayed peaks of the pure phase CuCrO2 structure as hexagonal delafossite-type structure space group: Rm. The Seebeck coefficient of the samples displayed positive sign as p-type (hole) conductor. The XPS results displayed Mg2+, Cu1+, Cr3+ and Cr4+ ion states. The Mg2+ induced mixed-valance Cr3+/Cr4+ states resulting in enhanced Seebeck coefficient due to a strong correlation of the spin-entropy. The experimental results of Seebeck value were close to calculated results by the extended Heikes formula confirming of the strong correlation effect. In addition, the Mg-doped CuCrO2 resulted in increased electrical conductivity and reduced thermal conductivity with increasing temperature. These indicate that the Mg2+-substituted for Cr3+ of CuCrO2 delafossite enhance the thermoelectric properties. © 2015
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Preparation, characterization and finite element computation of Cu(Al 1/2Fe1/2)O2 Delafossite-oxide themoelectric generator module
(2014-09-02)
Ruttanapun, Chesta
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Jindajitawat, Phumin
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Buranasiri, Prathan
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Naenkieng, Daengdesh
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Boonyopakorn, Narongchai
The CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> delafossite oxide has been synthesized by solid state reaction method for studying thermoelectric properties and measuring thermoelectric generator output electric power. The Finite Element technique was used to compute the output voltage of thermoelectric generator in applying temperature difference on a single bar and a module model with compared to the measurement results. The measurement results of positive sign Seebeck coefficient confirm the p-type conductor of the sample. The properties of Seebeck coefficient, electrical conductivity, and thermal conductivity are range from 260 to 310V/K, from 7 to16 S/cm and from 2.5 to 3.5 W/cm-K,respectively, in the temperature range of 300 to 960 K. The output voltage of the single bar in dimension 4.2 × 2.5 × 20 mm 3 obtained 0.5 to 3 mV on applying temperature difference from 1 to 10 K closely to the Finite Element result. The computing results of the thermoelectric single bar and module in high temperature reveal the output electric voltage of CuAl<inf>1/2</inf>Fe<inf>1/2</inf>O<inf>2</inf> oxide raises with the temperature and the number of thermoelectric leg increase. In important results, the high value of electric voltage is obtained 0.2 and 0.4 V for the single bar and the module at 950 K. © 2014 Taylor & Francis Group, LLC.
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High temperature thermoelectric properties of delafossite CuBO2
(2014-01-01)
Ruttanapun, Chesta
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Jindajitawat, Phumin
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Buranasiri, Prathan
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Thowladda, Warawoot
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Neeyakorn, Worakarn
CuBO<inf>2</inf> is prepared by a solid-state reaction method to investigate thermoelectric properties in high temperature. The XRD result confirms the CuBO<inf>2</inf> compound existing in this method. The Seebeck reveals the compound displays p-type thermoelectric material. The experimental results of electrical resistivity exhibited results of 0.004 S/cm to 0.038 S/cm with the temperature range of 650 to 830 K. The Seebeck value is in the range of 450 μV/K to 950 μV/K, and the thermal conductivity is in the range of 1.4 × 10-5 to 5.3 × 10-5 W/m-K2 with the same temperature. The maximum PF and ZT is 5.3 × 10-5 W/m-K2 and 0.0016, respectively, at 960 K. This work demonstrates that the CuBO<inf>2</inf> delafossite-oxide compound displays the p-type thermoelectric materials. © 2014 IEEE.
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Reinvestigation thermoelectric properties of CuAlO2
(2014-01-01)
Ruttanapun, Chesta
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Kosalwat, Wattana
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Rudradawong, Chalermpol
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Jindajitawat, Phumin
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Buranasiri, Prathan
Bulk CuAlO2 delafossite has been synthesized by solid state reaction to reinvestigate the thermoelectric properties. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured in a high temperature range of 300 to 960 K. The result of positive sign of Seebeck coefficient confirms p-type nature of CuAlO2 compund. The results of bulk sample for Seebeck coefficient, the electrical conductivity and thermal conductivity are range of 900 to 300 μV/K, of 0.01 to 2 S/cm, and of 3.5 W/mK to 1.5 W/mK. The maximum ZT value of bulk sample is 0.017 at a 960 K. These results can be concluded that the bulk CuAlO2 by solid state state displays thermoelelctric material.
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Thermoelectric properties of Sn2+-substituted CuFeO2 delafossite-oxide
(2013-10-29)
Ruttanapun, Chesta
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Jindajitawat, Phumin
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Thowladda, Warawoot
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Neeyakorn, Worakarn
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Thanachayanont, Chanchana
This study aims to investigate the effect of the Sn2+-substituted into the CuFeO<inf>2</inf> delafossite on thermoelectric properties in the Sn content of x = 0.03, 0.05. The CuFe<inf>1-x</inf>Sn<inf>x</inf>O<inf>2</inf> samples were synthesized by solid state reaction. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured in the range of 300 to 960 K. The Seebeck coefficient display positive sign in all temperature range and the XPS show the stable Sn+2 state as confirming the Sn-doped CuFeO<inf>2</inf> playing p-type conductor. The Sn2+-substituted supports the mixed valency Fe3+/Fe4+ state in transition octahedral oxide of FeO<inf>6</inf> layer enhancing Seebeck coefficient. The high Seebeck are appeared in content of x=0.03 which are 280 to 340 μV/K in the range of 300 to 800 K. The experimental Seebeck corresponds to the prediction formula at high temperature. Totally, the maximum Power Factor is 2.30×10-4 W/mK2 occurring in the CuFe<inf>0.95</inf>Sn<inf>0.05</inf>O<inf>2</inf> at 860 K which is higher than that value of the undoped-CuFeO<inf>2</inf> in 4 times. These support that the Sn-substituted CuFeO<inf>2</inf> delafossite enhancing thermoelectric properties. © (2013) Trans Tech Publications, Switzerland.
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Reinvestigation the thermal and electrical transport properties of Tl7Sb2
(2013-10-29)
Charoenphakdee, Anek
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Harnwunggmoung, Adul
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Seetawan, Tosawat
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Rattanapun, Chesta
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Amornkitbamrung, Vittaya
The authors examined the thermal and electrical transport properties of Tl<inf>7</inf>Sb<inf>2</inf> at temperatures ranging from room temperature to 400 K. The crystal system of Tl<inf>7</inf>Sb<inf>2</inf> is cubic with the lattice parameter a = 1.16053 nm and the space group is Im3m. The polycrystalline samples were prepared by melting stoichiometric amounts of thallium and antimony. Although, usually the thermal conductivity of thallium compounds is very low (<1 Wm-1K-1), that of Tl<inf>7</inf>Sb<inf>2</inf> was relatively high (~13 Wm-1K-1 at room temperature). This is because of the large electronic contribution to the thermal conductivity. © (2013) Trans Tech Publications, Switzerland.
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Synthesis and thermoelectric properties of Cu0.95Pt 0.05Fe0.97Sn 0.03O2 delafossite-oxide
(2013-01-01)
Ruttanapun, Chesta
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Boonchom, Banjong
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Vittayakorn, Naratip
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Harnwunggmoung, Adul
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Charoenphakdee, Anek
The Cu<inf>0.95</inf>Pt<inf>0.05</inf>Fe<inf>0.97</inf>Sn0.0 <inf>3</inf>O<inf>2</inf> delafossite sample, which is the simultaneous substitution of the Pt for Cu sites and the Sn for Fe sites of CuFeO<inf>2</inf> delafossite, has been investigated the simultaneous effect on electrical conductivity and Seebeck Coefficient for thermoelectric materials due to the previous reports of Cu<inf>0.95</inf>Pt<inf>0.05</inf>FeO<inf>2</inf> compound displaying high enhancement effect of electric conductivity and the CuFe <inf>0.97</inf>Sn0.0<inf>3</inf>O<inf>2</inf> exhibiting large increasing of Seebeck coefficient. The sample of Cu<inf>0.95</inf>Pt<inf>0.05</inf>Fe <inf>0.97</inf>Sn0.0<inf>3</inf>O<inf>2</inf> was synthesized by solid state reaction method. The crystal structure was characterized by XRD, and the valency oxidation state of the sample was evaluated by XPS. The electrical conductivity, Seebeck coefficient, and thermoelectric conductivity were measured in the high temperature range of 320 to 860 K. The measurement results show that, the sign of Seebeck value and result of XPS reveal the sample displaying p-type thermoelectric materials as confirming the simultaneous Pt and Sn-substituted contributing hole carrier. For the effect of simultaneous substitution, the Seebeck coefficient is enhanced in temperature lower than 650 K, while electrical conductivity displays small value in all temperature range. In surprising value, the thermal conductivity of the sample is smallest value in all temperature range. Totally, the ZT value of sample is obtained 0.07 at 860K as higher than that of the reference-based. This experiment confirms that the simultaneous Pt-doped and Sn-doped of Cu<inf>0.95</inf>Pt<inf>0.05</inf>Fe <inf>0.97</inf>Sn0.0<inf>3</inf>O<inf>2</inf> compound show high ZT value in temperature higher than 700 K. © 2013 Copyright Taylor and Francis Group, LLC.
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Thermoelectric properties of Cu1-xPtxFeO2 (0.0 ≤ x ≤ 0.05) delafossite-type transition oxide
(2011-03-31)
Ruttanapun, Chesta
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Wichainchai, Aree
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Prachamon, Wutthisak
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Yangthaisong, Anucha
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Charoenphakdee, Anek
The samples of Cu<inf>1-x</inf>Pt<inf>x</inf>FeO<inf>2</inf> (0 ≤ x ≤ 0.05) delafossite were synthesized by solid state reaction method for studying thermoelectric properties. The properties of Seebeck coefficient, electrical conductivity and thermal conductivity were measured in the high temperature ranging from 300 to 960 K. The results of Seebeck coefficient, electrical conductivity and power factor were increased with increasing Pt substitution and temperature. The thermal conductivity was decreased from 5.8 to 3.5 W/mK with increasing the temperature from 300 to 960 K. An important results, the highest value of power factor and ZT is 2.0 × 10-4 W/mK2 and 0.05, respectively, for x = 0.05 at 960 K. © 2011 Elsevier B.V. All rights reserved.

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