High-temperature thermoelectric properties of Ag x Y y Ca2.8Co4O9 + δ ceramics

Abstract

Thermoelectric ceramics, Ag x Y y Ca 2⋅8 Co 4 O 9 + δ (0 ≤ x, y ≤ 0⋅15), have been prepared using a sol-gel method, followed by pressureless sintering. The phase structures and microstructures of oxides were investigated at room temperature. Thermoelectric properties including Seebeck coefficient, electrical conductivity and thermal conductivity were measured from 303 to 973 K. It was found that the samples contain nanostructured Ag phase with grain size of 100 nm. The Ag 0⋅05 Y 0⋅15 Ca 2⋅8 Co 4 O 9 + δ sample has the maximum figure of merit (ZT ~ 0⋅14 @ 973 K), which is about 27% higher than that of Ca 3 Co 4 O 9 + δ .

Thermoelectric properties of barium doped calcium cobaltite obtained by simplified chemical route

“…where σ 0 is the pre-exponential term and E a is the Arrhenius activation energy. Linear relationships can be obtained at two temperature ranges: below 600 K, representing the small polaron-hopping conduction mechanism [15]; and above 600 K, indicating the semiconducting mechanism. As shown in Fig.…”

“…Many approaches regarding the enhancement of TE performance of calcium cobaltite (CCO) are conveyed through doping with alkaline metals [8,9], alkaline earth metals [10][11][12][13], transition metals [14,15], and/or rareearth metals [16] at Ca site. A comparison between some synthetic routes in the obtention of Ca 3 Co 4 O 9 phase shows that attrition milling and chemical methods produce very reactive precursors, reflected in the decomposition of CaCO 3 after a single heat treatment at 1023 K for 12 h. The attrition milling and the classical solid-state methods still contain small amounts of Ca 3 Co 2 O 6 phase while the chemical method can produce near pure Ca 3 Co 4 O 9 phase [17].…”

Raising Nanofiber Output: The Progress, Mechanisms, Challenges, and Reasons for the Pursuit

“…Zheng and Zeng utilized a concentric multihole spinneret. [80] When this side of the spinneret bearing holes had a basic flat surface, simulation study showed relatively lower electric field distribution in the central area compared to that toward the edges. Modifying the spinneret by creating a protrusion in the central area greatly boosted the electric field distribution to the central area.…”

“…Reproduced with permission. [80] Copyright 2014, Springer. Cutaway view showing the cylindrical porous tube with its axis oriented vertically within a coaxial cylindrical collector (not to scale) b).…”

Research Progress of the Preparation of Nano-Ferric Oxide

“…For example, Zheng et al 23 reported to use the hydrothermal method to prepare the Fe3O4 nano-particle with the particle size of 27 nm with the surface active agent of AOT. This kind of particle has super-paramagnetism under room temperature.…”