New method to improve the grain alignment and performance of thermoelectric ceramics

Abstract

Textured Bi 2 Ca 2 Co 1.7 O x ceramic rods were obtained by Electrically Assisted Laser Floating Zone (EALFZ) technique. The polarity effects of an external current, applied during the laser floating zone growth, have been investigated.Microstructure and thermoelectric properties have been studied and correlated with the current polarity. An important improvement of power factor was obtained for samples grown with the positive pole connected to the seed. This result evidences the advantages of EALFZ technique as a potential method for obtaining high performance thermoelectric materials.

Influence of Ca substitution by Mg on the Ca₃Co₄O₉ performances

“…Such processes allow the alignment of the conducting planes producing macroscopic properties comparable to the obtained on single crystals, by decreasing electrical resistivity. Numerous methods have been reported to be efficient in producing well aligned bulk materials, in these or in similar anisotropic systems, such as hot uniaxial pressing [13], spark plasma sintering (SPS) [14], microwave texturing [15], laser floating zone melting (LFZ) [16,17], electrically asisted laser floating zone (EALFZ) [18,19], templated grain growth (TGG) [20], etc. The main advantage of these techniques is the production of materials with very low electrical resistivity values due to the preferential alignment of conducting planes with the current flow 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].…”

Effect of Ga addition on Ca-deficient Ca3Co4Oy thermoelectric materials

“…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 [15], templated grain growth (TGG) [16], spark plasma sintering [17], microwave texturing [18], laser floating zone melting (LFZ) [19], electrically assisted laser floating zone [20], etc. On the other hand, these methods possess some drawbacks due to different factors, as the relatively long treatments required for the first two ones, or the high costs associated with the equipment and the strong dependence of thermoelectric properties on the growth or the texturing speeds for the other ones [13,18,[21][22][23].…”