Nanocrystalline Thermoelectric Ca₃Co₄O₉ Ceramics by Sol−Gel Based Electrospinning and Spark Plasma Sintering

Abstract

A novel technique is developed to process nanocrystalline Ca3Co4O9 ceramics with much enhanced thermoelectric properties. Nanocrystalline Ca3Co4O9 nanofibers are synthesized first using sol−gel based electrospinning, and then consolidated into bulk ceramics by spark plasma sintering with preferred grain orientation distribution and without substantial grain growth. The nanofiber-sintered ceramic has a grain size much smaller than that sintered from sol−gel synthesized powders with improved texture, and has simultaneously enhanced Seebeck coefficient, electric conductivity, and thermal resistivity, resulting in substantial enhancement in thermoelectric figure of merit ZT. This technique is promising for high-efficiency thermoelectric conversion of waste heat directly into electricity.

Electrospun Hierarchical CaCo2O4 Nanofibers with Excellent Lithium Storage Properties

“…+ ions between the layers. [34,38,39] This unusually layered structure makes it useful for Li diffusion.…”

“…Moreover, although Ca 3 Co 4 O 9 [39,40] has been prepared by electrospinning techniques and exhibits enhanced thermoelectric properties, to the best of our knowledge, the synthesis of CaCo 2 O 4 with 1D hierarchical nanostructures as well as their application in LIBs remains unreported. Herein, we demonstrate the preparation of 1D hierarchical CCO-NFs, which are composed of ultrathin nanoplates, by electrospinning and controlled calcination.…”

Variations of the Thermoelectric Characteristics of ZnO Nanofibers from the Use of a Thermal Treatment

“…Most NFs have been prepared with electrospinning and a subsequent thermal treatment, the latter of which affects the NF diameter and the residual-polymer quantity. Over time, heating-temperature and cooling-rate adjustments have been attempted to form oxide NFs with high thermoelectric efficiencies [7,8]; nevertheless, a dearth of studies regarding the effect of the heating time on the thermoelectric characteristics exists.…”

“…In terms of the fabrication of thermoelectric modules that are composed of n-type and p-type NF couples, n-type oxide NFs are important; however, a paucity of studies regarding the n-type oxide NFs presently exists, while the p-type oxide NFs including ptype Ca 3 Co 4 O 9 and p-type LaSrCoO 3 have been widely researched [6][7][8][9][10]. In this study, n-type ZnO thermoelectric NFs are therefore prepared, and the heating-time-based variations of the thermoelectric characteristics of these ZnO NFs are examined.…”

High-throughput synthesis of thermoelectric Ca3Co4O9 films

“…For these reasons, several nanostructured thermoelectric materials have been developed, including as nanowires, superlattices, and nanocomposites. 2,3 Among potential oxide thermoelectric materials, the layered cobalt oxide Ca 3 Co 4 O 9 is particularly interesting. Ca 3 Co 4 O 9 can be denoted as ½Ca 2 CoO 3 RS ½CoO 2 1:62 to highlight the two layers that constitute the misfit structure and the ratio of the differing b-axis parameters.…”