Abstract
Ca3 Co4 O9 is a potential high temperature thermoelectric material. We explore the hydrothermal treatment improved sol-gel method to prepare Ca3 Co4 O9 thermoelectric materials. We find that this treatment can increase the thermoelectric performance of the samples compared with the conventional citric acid sol-gel method. We also find the samples prepared by the improved sol-gel method have more uniform grain distribution, better densification, and less voids. At about 1000K, compared with the conventional sol-gel method, the power factor of the samples prepared by improved sol-gel method improves about 168%.
Highlights
In recent years, due to the need of environmental protection and energy saving, thermoelectric materials have been paid more and more attention[1]
The samples prepared by sol-gel method and hydrothermal method have a smaller grain size and more uniform distribution relative to the solid state reaction method, and these two factors are considered to be the key to improve the thermoelectric performance[10]
We speculate that the solution environment at high temperature and high pressure has an effect on the property of the samples
Summary
Due to the need of environmental protection and energy saving, thermoelectric materials have been paid more and more attention[1]. In the solid state reaction, Ca3Co4O9 is obtained directly at high temperature from the dry mixture of CaO and CoO in a stoichiometric ratio(3:4). This method is simple but the grain size is big and the reaction temperature has a great influence on the composition of final product. The samples prepared by sol-gel method and hydrothermal method have a smaller grain size and more uniform distribution relative to the solid state reaction method, and these two factors are considered to be the key to improve the thermoelectric performance[10]. The composition, structure and micromorphology of the samples prepared by improved sol-gel method are investigated by comparing with those of the conventional method. The thermoelectric performance of the samples is investigated as well
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