Granular and Lamellar Thermoelectric Oxides Consolidated by Spark Plasma Sintering

Abstract

Using the spark plasma sintering (SPS) technique, dense nanostructured Ca 0.95 Sm 0.05 MnO 3 (n-type) and textured Ca 3 Co 4 O 9 (p-type) ceramics were prepared. Nanoceramic powders of doped n-type were synthesized using two routes: coprecipitation and solid-state reaction. The SPS method has been used to control the samples' densification and grain growth. Microstructural investigations reveal that the SPS technique results in high bulk density and homogeneous morphology for Ca 0.95 Sm 0.05 MnO 3 , and grain alignment for Ca 3 Co 4 O 9 . The thermoelectric and mechanical properties were investigated, showing a dependence on the starting grain size and being governed by the SPS conditions.

Enhancement of Ca 3 Co 4 O 9 thermoelectric properties by Cr for Co substitution

“…Such processes should allow the alignment of the conducting planes leading to macroscopic properties comparable to those obtained on single crystals. Numerous methods have been reported to be efficient to produce well aligned bulk materials, in these or in similar anisotropic systems, such as hot uniaxial pressing [17], spark plasma sintering [18], microwave texturing [19], laser floating zone melting (LFZ) [20], templated grain growth (TGG) [21], etc. The main advantage of these techniques is the production of materials with very high electrical properties due to the preferential conducting plane alignment with the conduction direction.…”

Processing effects on the thermoelectric properties of Bi₂Ca₂Co_1.7O_x ceramics

“…Some techniques have been shown to be adequate to obtain a good grain orientation in several oxide ceramic systems, as Template Grain Growth (TTG) [18], Spark Plasma Sintering (SPS) [19], laser floating zone melting (LFZ) [20], or electrically assisted laser floating zone (EALFZ) [21].…”

Growth and thermoelectric properties of CaMnO3-based thin films

“…The distortions are commonly described by tilts of the MnO6 octahedra as seen in figure 2.1 (b). The most common synthesis method of CaMnO3 is a solid state reaction, but there are studies where other synthesis methods are explored, such as; a gas phase reaction synthesis, 24 chemical coprecipitation method, 25,26 glycine-nitrate synthesis, 27,28 electrostatic spray deposition, 29 and soft chemistry synthesis. 30,31 Many of these synthesis techniques have proven successful for synthesising CaMnO3 with improved ZT compared to the solid state reaction method.…”