Preparation of Well-Tiled γ-Na x Co2O4 by a Novel and Simple Sodium Alginate Gel Method and Its Electrical Properties

Abstract

In this paper, a novel and simple sodium alginate (SA) gel method was developed to prepare c-Na x Co 2 O 4 . This method involved the chemical gelling of SA in the presence of Co 2+ ions by cross-linking. After calcining at 700°C to 800°C, single-phase c-Na x Co 2 O 4 crystals were obtained. The arrangement of about 1 lm to 4 lm flaky particles exhibited a well-tiled structure along the plane direction of the flaky particles. SA not only acted as the control agent for crystal growth, but also provided a Na source for the c-Na x Co 2 O 4 crystals. The electrical properties of c-Na x Co 2 O 4 ceramics prepared via ordinary sintering after cold isostatic pressing were investigated. The Seebeck coefficient and power factor of the bulk material were 177 lV K À1 and 4.3 9 10 À4 W m À1 K À2 at 850 K, respectively.

Scalable nanomanufacturing of millimetre-length 2D NaxCoO2 nanosheets

“…3b). Similar behavior was observed by Zhang et al 27 for alginate gel based synthesis of tiled Na x Co 2 O 4 crystals. The entrapment and crosslinking by PAA is crucial for forming the autocombusted flakes: if citric acid is used in place of PAA and the ratio of carboxylic moieties to the number of metal cations is fixed (2 : 1), flake-like formations do not occur after autocombustion and the volume of the autocombusted form is much smaller compared to the case with PAA (i.e., less than 1/3).…”

Synthesis and Electrical Properties of γ-Na x Co2O4 via a Citrate Sol–Gel Method with Polyethylene Glycol 400

“…[2][3][4][5] Research results have shown that the thermoelectric properties of polycrystalline sintered bulk NaCo 2 O 4 can be improved by obtaining more highly oriented crystals. 2,3 Furthermore, properties of NaCo 2 O 4 powders such as the particle size and the morphology, which are determined by the preparation technology applied, [6][7][8][9] are related to the thermoelectric properties of polycrystalline sintered bulk Na x Co 2 O 4 .…”