A. Hmood

Significant Influences of Selenium on the Electrical Properties of Bi2Te3 Compounds Synthesized Using Solid-State Microwave Irradiation

The thermoelectric materials based on p-type Bi2Se3xTe3 (1-x) bulk products and dispersed with x compositions of Se (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were fabricated using standard solid-state microwave synthesis procedures. The products were characterized by X-ray diffraction (XRD). The XRD characterizations revealed that these products are pure Bi2Te3 and Bi2Se3 with uniform structures. The electrical properties of the Bi2Te3, Bi2Se3 and Bi2Se3xTe3 (1-x) samples were measured in the temperature range of 303–523 K. The highest value of the Seebeck coefficient was 176.3 μV/ K for the Bi2Se0.6Te2.4 sample, but only 149.5 and 87.4 μV/K for the Bi2Te3 and Bi2Se3 samples, respectively.

Fabrication and Characterization of Pb1-xYbxSe0.2Te0.8 Based Alloy Thin Films Thermoelectric Generators Grown Using Thermal Evaporation Method

In the current work p-Pb0.925Yb0.075Te:Te and n-Pb0.925Yb0.075Se0.2Te0.8 powders synthesized by solid-state microwave route were used to fabricating thermally evaporated thin films. The micro-thermoelectric devices were composedof 20-pairs and 10-pairs p-Pb0.925Yb0.075Te:Te and n-Pb0.925Yb0.075Se0.2Te0.8 thin films on glass substrates. Overall size of the thin films thermoelectric generators which consist of 20-pairs and 10-pairs of legs connected by aluminumelectrodes were 23 mm×20 mm and 12 mm×10 mm, respectively. The 20-pairs p–n thermocouples in series device generated output maximum open-circuit voltage of 275.3 mV and a maximum output power up to 54.4 nW at temperature difference ∆T= 162 K, and 109.4 mV and 16.7 nW at ∆T=162 K, for 10-pairs, respectively.

Effect of Selenium on Structure and Electrical Property for Bi0.4Sb1.6Se3xTe3(1-x) Novel Hexagonal Rods

Novel hexagonal rods of Bi0.4Sb1.6Se3xTe3(1-x) (0.0≤x≤1.0) were synthesized successfully through solid-state microwave synthesis. These hexagonal rods were explored using field emission scanning electron microscopy images. The X-ray diffraction results indicate that the powders (0.0≤x≤0.8) can be indexed as the rhombohedral phase, whereas the sample with x=1.0 has an orthorhombic phase structure. The electrical conductivity gradually decreases as Se increased, resulting in an increase in the Seebeck coefficient. Ascribing to the increased Seebeck coefficient for the sample with x=0.8, the maximum power factor is 7.47 mW/mK2 at 373 K.

Structural and Thermoelectric Properties of Bi0.4Sb1.6Se3xTe3(1-X) Quaternary Compound

Novel hexagonal rods of Bi0.4Sb1.6Se3xTe3(1-x) (0.0x1.0) were synthesized successfully through solid-state microwave synthesis. These hexagonal rods were explored using field emission scanning electron microscopy images. The X-ray diffraction results indicate that the powders (0.0x0.8) can be indexed as the rhombohedral phase, whereas the sample with x=1.0 has an orthorhombic phase structure. The electrical conductivity gradually decreases as Se increased, resulting in an increase in the Seebeck coefficient. Ascribing to the increased Seebeck coefficient for the sample with x=0.8, the maximum power factor is 7.47 mW/mK2 at 373 K.

Structural and Electrical Properties of Pb1-xYbxSeyTe1-y Quaternary Compound Synthesized by Solid State Microwave Assisted Plasma

Solid-state microwave as a method was used to synthesize quaternary compounds Pb1-xYbxSe0.2Te0.8 from initial components to obtain polycrystalline ingots with large grain size. Thin films of Pb1-xYbxSe0.2Te0.8 were then deposited onto glass substrates using thermal evaporation in vacuum, which have a polycrystalline rock salt (NaCl) structure for powders, and thin films. The field emission scanning electron microscopy (FESEM) images reveal that the Pb1-xYbxSe0.2Te0.8 thin films with Yb-doped have uniform crystal grain size and dense nanostructure. The thermoelectric properties of thin films were measured in the temperature range 298–523 K. The Seebeck coefficient of films increased with x when x=0.015, 0.03 and 0.045, while decreased for x=0.06−0.105.