Study On Preparing And Thermoelectric Properties Of Ca₃Co₄O₉ And Cl Ion Adoped Thermoelectric Material

Thermoelectric material is a kind of functional material converting heat energy directly to electric energy, thermal energy and electrical energy. Thermoelectric material is becoming a topical research aspect because of ascendancies in the environment, energies and the utilization of materials.In this work, the thermoelectric phenomena, history, the use and the recent development progress of thermoelectric materials are reviewed in detailed at first.We have selected calcium cobalt oxide (Ca₃Co₄O₉) as our research object. In the experiments, analytically pure CaCO₃ and CO₂O₃ were used as raw material,CaCO₃ and adoping Cl ion thermoelectric material were fabricated by pressless sintering and hot pressure sintering. The microstructures of the samples were characterized by XRD,SEM,EDX et al. The relative density and Pore number were measured too. The thermoelectric properties were determined by measuring electrical resistivity,seebeck coefficient and power factor. At the same time, we compared blank sample with adoping sample and compare pressless sintering with hot pressure sintering.The results show that: high Purity Ca₃Co₄O₉ and Ca₃Co₄O₉ doped with Cl ion prepared by pressless sintering and hot pressure sintering. SEM photo shows that the microstructure of the production was plate-like and majority of grain. The material indicates evident anisotropy . hot pressure sintering production was more compact and uniformity in the microstructure. Both of two preparation methods, the electrical resistivity of sample was reduced follow the increasing temperature, while reducing more obviously in high temperature. It shows that material was fit for using in high temperature. The seebeck coefficient of sample was increased follow the increasing electrical conductivity. It considers as causing by tractive phonon. Both of two preparation methods, The seebeck coefficient and electrical conductivity was increased obviously by adoping Cl ion. When adoping amount of CaCl₂ was 0.5%, The seebeck coefficient of pressless sintering production was reached maximum of 113μV/K, increased 13% compared with that before being adoped. The electrical resistivity of sample was reached minimum of9.14×10^-5Ωm, reduced 14% compared with that before being adoped. The seebeck coefficient of hot pressure sintering production was reached maximum of 126μV/K, increased 11% compared with that before being adoped. The seebeck coefficient of sample was reached minimum of 8.47×10^-5Ωm, reduced 7% compared with that before being adoped. It indicates that to improve thermoelectric property by adoping was feasible. In the contrastive experiment of pressless sintering and hot pressure sintering, the hot pressure sintering production excelled pressless sintering production in the thermoelectric property and microstructure.