Investigation On The Preparation And Properties Of NaCo₂O₄ Based Thermoelectric Material

Thermoelectric material is a kind of functional material converting heat energy directly to electric energy. Devices made of thermoelectric material have many special advantages, and have been successfully used in a few acmes of science and technology. In the present work, the development in thermoelectric materials were reviewed and discussed. Recently, Oxide thermoelectric materials were found to have high working temperature, oxidation-resistant, no pollution, simple preparation, long life, and have become new candidate materials with a potential to study and applying values. In this paper, Oxide NaCo₂O₄ has been selected as this study due to very good thermoelectric performance. A new series of oxides were synthesized by the substitution and their thermoelectric properties were investigated.In this work, NaCo₂O+4 doped with K, Ca, Sr, Ce in Na position by solid state reaction and sol-gel methods in the first time, and NaCo₂O₄ doped by Ti, Ni, Cr in Co position by hot-pressed sinter and cool-pressed sinter were prepared, and electrical conductivity and Seebeck coefficients of the materials were measured, as well as the effects of doping elements, doping amount and preparing methods were also investigated to optimize the preparation of the materials.The main achievements of the work are followings:(1) High purity NaCo₂O₄ doped with K, Ca, Sr was prepared by both solid state reaction and sol-gel method. Power factor of NaCo₂O₄ prepared by sol-gel method is higher than that by solid-state reaction method.(2) Power factor of NaCo₂O₄ was increased by doping K, Ca and Sr and decreased by Ce. Power factor of (Na_0.9Sr_0.1)_1.6Co₂O₄ prepared by sol-gel method is 2.26×10^-4W·m^-1·K^-2 and the highest, increased 49.7% compared with that before...