Characterization of Thermoelectric Metal Oxide Elements Prepared by the Pulse Electric‐Current Sintering Method

Abstract

Thermoelectric elements consisting of the layered polycrystalline materials of Al‐doped ZnO and NaCo2O4 were prepared using the pulse electric‐current sintering (PECS) method at 900°C for 3 min. Direct contact between the polycrystalline Al‐doped ZnO and the NaCo2O4 was obtained in a single‐step process for the stacked powders. The electrical conductivities of the polycrystalline materials prepared by PECS were higher than those of materials prepared by conventional sintering, despite their porous structure. The thermoelectric voltage of the 1‐mol%‐Al‐doped ZnO and NaCo2O4 polycrystalline element (measuring ∼6 mm × 3 mm × 15 mm) was 83 mV at dT= 500 K, when the junction of the elements was at 800°C.

A study on thermoelectric performance and magnetic properties of Ti-doped Bi2Sr2Co1.8Oy ceramic materials

“…The first one is associated with entropy, in which a disordered crystal structure provides high ZT, and the second one to the crystal lattice energy, meaning that S rises with temperature, leading to larger Z at higher temperatures [18]. Finally, electrical properties are affected by structural and microstructural features, as grain alignment and density through different techniques as reported in previous works [19][20][21][22]. For this reason, texturing techniques [23,24], or synthesis methods [25,26] can be applied to enhance electrical properties and lead to closer performances to those measured in single crystals.…”

Transition metal oxides – Thermoelectric properties

“…Ni and Ti to achieve improved TE properties. Al is the most common dopant for ZnO [83][84][85][86][87][88][89][90][91][92][93][94]. Generally, Al doping increases the carrier mobility and reduces the phonon mean free path in the crystal lattice of ZnO, resulting in higher σ and lower κ.…”

“…Hence, doping, compositing and processes altering the oxygen deficiency can be implemented to achieve the desired thermal conductivity. Conversely, in thermopower wave Such dopants result in enhanced TPFs in TMOs such as ZnO and CoO2, which will be discussed in details in sections 4.4 and 4.7 respectively[83][84][85][86][87][88][89][90][91][92][93][94][95] [96].After incorporating dopants and altering the stoichiometry, the most challenging issue is the determination of electronic band structures[70]. Theoretical methods such as density functional theory (DFT) can help; however, underestimation of the band gap by DFT calculations generally results in inaccuracy of theoretical predictions of the Seebeck coefficient and the bipolar effect[70].…”

Waste Thermal Energy Harvesting (I): Thermoelectric Effect

“…Sr addition can reduce thermal conductivity of Ca 3 Co 4 O 9 , which leads a slight increase in the figure of merit. Na x CoO 2 is another important layered cobaltite based thermoelectric oxide [158][159][160][161][162][163][164]. The variation in properties of Na x CoO 2 is large than that of Co 3 Co 4 O 9 , Na content can be varied in a wide range.…”