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    Synthesis of Zn0.96Al0.04O thermoelectric material for fabrication of thermoelectric module and thermoelectric generator
    (2018-01-01)
    Chanprateep, S.
    ;
    The main objective of this work is aim to synthesize Zn<inf>0.96</inf>Al<inf>0.04</inf>O thermoelectric materials for fabricating thermoelectric modules and inventing thermoelectric generator. The Zn<inf>0.96</inf>Al<inf>0.04</inf>O sample was prepared by a conventional solid state reaction method. The formation of structure was proved by X-ray diffraction and the thermoelectric properties were measured. The results presented that the Zn<inf>0.96</inf>Al<inf>0.04</inf>O displayed thermoelectric materials and showed the thermoelectric properties as higher than that of ZnO based. The Zn<inf>0.96</inf>Al<inf>0.04</inf>O thermoelectric modules displayed the electric power was increased with number of module, large temperature difference and operation at high temperature. The Zn<inf>0.96</inf>Al<inf>0.04</inf>O thermoelectric generator showed high performance for electric generator at high temperature. The sixteen Zn<inf>0.96</inf>Al<inf>0.04</inf>O legs thermoelectric generator can generate electric power 1.4 mW at 800 in ΔT = 600 C. Thus, the Zn<inf>0.96</inf>Al<inf>0.04</inf>O thermoelectric material can be used for application of thermoelectric generator at high temperature.
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    Item type:Publication,
    Reinvestigation thermoelectric properties of CuAlO2
    (2014-01-01) ;
    Kosalwat, Wattana
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    Jindajitawat, Phumin
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    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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    Item type:Publication,
    Effects of Pd substitution on the thermoelectric and electronic properties of delafossite Cu1-xPdxFeO2 (x=0.01, 0.03 and 0.05)
    (2014-07-01)
    Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> (x=0.01, 0.03 and 005) delafossite was prepared by solid state reactions and was calcined/sintered at 1050 °C. The effect of Pd<sup>2+</sup> substitution for the Cu<sup>1+</sup> sites on the thermoelectric and electronic properties of Cu <inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> were investigated. The crystal structure, oxygen decomposition, thermoelectric and electronic properties were characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), Seebeck coefficient, electrical conductivity and thermal conductivity measurements. The characterization showed that Cu <inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> formed a hexagonal delafossite structure with R3-m symmetry. The existence of Pd<sup>2+</sup>, Cu<sup>1+</sup>, Cu<sup>2+</sup>, Fe<sup>3+</sup>, Fe<sup>4+</sup> and O was revealed from the XPS results. Confirmation of Pd<sup>2+</sup> substitution for the Cu <sup>1+</sup> sites occurred by increasing the c-axis in the lattice parameter with a Pd content. The O content intercalated at the center of the triangular Cu acted as a support to produce Cu<sup>2+</sup> ions and was reduced with an increasing Pd content. The mixed valencies of Cu<sup>1+</sup>/Cu<sup>2+</sup> and Cu<sup>1+</sup>/Pd<sup>2+</sup> in the Cu layer changed the electrical conductivity and the Fe<sup>3+</sup>/Fe<sup>4+</sup> mixed valencies in the FeO<inf>6</inf> layer caused the Seebeck coefficient to increase. Both the electrical conductivity and Seebeck coefficient for Pd contents of x=0.01 and 0.03 were higher than that of non-doped CuFeO<inf>2</inf>. The low thermal conductivity of Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> resulted from the substitution of Pd, which has a large atomic mass, into structure. The Jonker plot indicated that the electronic properties displayed a degenerate density of states and that Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> was a semiconductor. A high ZT value of 0.055 was obtained for a Pd content of 0.03 at 950 K. The Pd<sup>2+</sup> substitution for the Cu<sup>1+</sup> sites influenced the thermoelectric and electronic properties of the delafossite Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> samples. © 2014 Elsevier Inc.
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    Item type:Publication,
    High temperature thermoelectric properties of delafossite CuBO2
    (2014-01-01) ;
    Jindajitawat, Phumin
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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<sup>-5</sup> to 5.3 × 10<sup>-5</sup> W/m-K<sup>2</sup> with the same temperature. The maximum PF and ZT is 5.3 × 10<sup>-5</sup> W/m-K<sup>2</sup> 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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    Item type:Publication,
    Effect of grain boundary interfaces on electrochemical and thermoelectric properties of a Bi2Te3/reduced graphene oxide composites
    (2020-08-01)
    Thongsamrit, Wannisa
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    Maneesai, Keerati
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    Karaphun, Attaphol
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    Tuichai, Wattana
    The electrochemical and enhanced thermoelectric properties of pristine Bi<inf>2</inf>Te<inf>3</inf> and Bi<inf>2</inf>Te<inf>3</inf>/reduced graphene oxide (Bi<inf>2</inf>Te<inf>3</inf> + rGO) composites at 1%, 3% and 5% levels of rGO were synthesized via a simple ultrasonic method. The X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–vis spectrometry (UV–vis) and their electrochemical and thermoelectric properties were measured. The ultrasonic method succeeded in producing rGO nanosheets composited with Bi<inf>2</inf>Te<inf>3</inf> forming grain boundary interfaces of rGO with Bi<inf>2</inf>Te<inf>3</inf>. The resulting samples displayed a continuous network structure of rGO nanosheets in Bi<inf>2</inf>Te<inf>3</inf> + rGO composites for electrons in the conduction band of the Bi<inf>2</inf>Te<inf>3</inf> structure. Electrons were transferred to rGO nanosheets at the interface, contributing electron charge carriers in Bi<inf>2</inf>Te<inf>3</inf> + rGO composites. This indicates band alignment between Bi<inf>2</inf>Te<inf>3</inf> and rGO nanosheets. The Bi<inf>2</inf>Te<inf>3</inf> + rGO composites exhibited an increasing storage charge mechanism of electrical double layer capacitors with greater rGO contents. The Bi<inf>2</inf>Te<inf>3</inf> + rGO composites displayed negative a Seebeck coefficient for thermoelectric materials. The highest ZT value was 0.17 in the bulk 1% Bi<inf>2</inf>Te<inf>3</inf> + rGO composite. Improved electrochemical and thermoelectric properties of the Bi<inf>2</inf>Te<inf>3</inf> + rGO 1% composite resulted from the interaction of the grain boundary interfaces of rGO nanosheets with pristine Bi<inf>2</inf>Te<inf>3</inf> following the model of band alignment between Bi<inf>2</inf>Te<inf>3</inf> and rGO nanosheets.