| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2003: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
In recent year, our group carried out electronic doping to perovskite type oxide Cd_3TeO_6(Cd^<2+>,Te^<+6>) with outer electron configuration of 4d^<10>. As a result, the n type thermoelectric material, which had the most superior thermoelectric property ability for the oxide and excluded transition metal, was obtained. It is thought that, the characteristic of the material is caused by the structure that all of the positive ions have the same electron configuration of 4d^<10>. Therefore, we focused on Cd_2InSbO_6(group space, R-3), CdIn_2O_4(group space, Fd-3m) and Cd_2SnO_4(group space, Pbam), which all the positive ions were electron configurations of 4d^<10>, synthesized three kinds of pure compounds above-mentioned, analyzed the crystal structure and evaluated the electrical property effected by carrier doping. The three kinds of compounds which sintered in the air atmosphere all showed a smaller temperature dependence of electrical resistivity. In addition, in comparison with a s
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ample composed of an oxygen atmosphere, the electrical resistivity of a reduction treated sample had a good performance, it is thought that a carrier is the electron which produced by oxygen vacancy. A Seebeck coefficient of the three kinds of compounds was negative, and the power factor around room temperature was 10^<-5> Wm^<-1>K^<-2> order, this value is very big in comparison with a general oxide (10^<-7> order). As a result, it was known that the oxides which consisted of a positive ion with the same most outer electron configuration suffered from similar belt structure have a similar electrical property.
Polycrystalline Cd_<3-x-y>Cu_xA_yTeO6(A=Li,Na) samples were prepared by solid-state reaction, and their crystal structure and electrical properties were investigated. In Cd_<3-x>Cu_xTeO6 and Cd_<3-y>A_yTeO6(A=Li,Na), the maxim solubility of x and y was 0.15 and 0.15 for A=Li,0.05 for A=Na,respectively. For co-substituted samples Cd_<2.9-y>Cu_<0.1>Li_yTeO6 and Cd_<2.9-y>Cu_<0.1>Na_yTeO_6, the maxim solubility of x was the same as single substitution above-mentioned. The alkali-metal substituted samples Cd_<3-y>A_yTeO_6(A=Li,Na) showed a negative Seebeck coefficient, which indicates that the major conduction carriers are electron. On the other hand, the co-substituted samples Cd_<2.9-y>Cu_<0.1>A_yTeO_6(A=Li,Na) represented a positive Seebeck coefficient, and major conduction carriers were hole through substitution by cupper ions. Less
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