High-temperature thermoelectric properties of polycrystalline Zn1−x−yAlxTiyO ceramics

Transition metal oxides – Thermoelectric properties

“…A study on co-doped Zn0.97Al0.03−yTiyO has shown an enhancement in both σ and S, resulting in TPFs as high as 3.8×10 2 μW/m.K 2 for Zn0.97Al0.02Ti0.01O at 1073 K. [86] κ and ZT values of these samples have however not been reported. Ga doping has also been reported to improve TE properties of ZnO resulting in ZT values close to the best Al-doped ZnO ceramics [198].…”

“…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].…”

Microstructure and thermoelectric properties of Zn1−xAlxO ceramics fabricated by spark plasma sintering

“…In addition, it is apparent that the addition of Al 2 O 3 to ZnO significantly suppresses the grain growth, resulting in a microstructure with much finer grains when x Z0.03. This is because the added Al 2 O 3 suppresses the grain-boundary mobility, thus enabling the pores to stay attached to the moving grain boundaries during sintering [13]. Nevertheless, porous materials with fine grains may be good as thermoelectric materials because its thermal conductivity can be effectively reduced.…”

“…Particularly, Al-doped ZnO oxides have been considerably studied as a high-temperature thermoelectric material for its high power factor (S 2 s). However, the solid solubility of Al into ZnO is very limited, and it is often experienced that Al-doped ZnO solid solutions can be hardly obtained if one uses Al 2 O 3 and ZnO oxides particles as starting materials [10][11][12][13][14][15].…”