Study On Properties Of Strontium Titanate And Calcium Cobalt Oxide Composite Materials

Thermoelectric materials are new energy materials that can transform heat energy into the electrical energy each other by thermoelectric effect, which are very wide application perspective.SrTiO₃ powder was prepared by hydrothermal method and Ca₃Co₄O₉ powder and SrTiO₃ and Ca₃Co₄O₉ composite power were prepared by sol-gel method. Application hot-press sinter, the SrTiO₃-Ca₃Co₄O₉ composite materials by single phase SrTiO₃ and single phase Ca₃Co₄O₉ were prepared. The microstructure and phase composition of the samples were characterized by SEM, XRD, the density and porosity were measured by DTA-TG; It was determined by measuring resistance and thermal conductivity; its composite materials of Ag and La doped were researched on it.The results show that: SrTiO₃ powder is a small cube-type, even grain about 100nm, which is prepared by hydrothermal method The best preparation process are as follow: the concentration of hydrothermal media alkali is 1.0mol/L, reaction temperature is 175℃, thermal insulation time is 45min. Ca₃Co₄O₉ powder of preparation by sol-gel method is a lamellar structure, grains size uniformity. The preparation processes are as follows: the n(D)/n(Mn+) is 2.90: 1, pH value is about 1.5, calcium cobalt ratio is 3: 4, reaction temperature is 700oC and thermal insulation time is 4h.SrTiO₃-Ca₃Co₄O₉ composite materials have good thermoelectric properties, the density is 3.27g·cm^-3, the porosity is 24.47%, the resistance is 47.1Ω; while the single Ca₃Co₄O₉ sintering density is 2.99g·cm^-3, the porosity is 26.55%, the resistance is 64.8Ω. SrTiO₃-Ca₃Co₄O₉ composite materials could reduce the material resistance and improve electrical conductivity of material effectively, and then improve the thermoelectric properties of materials. Doped results show that: the volume of Ag-doped is about 0.04g, the resistance is a minimum 12.28Ω; the volume of La-doped is 0.12g, the resistance is a minimum 19.55Ω. The doped could also increase the conductivity of material, improve the thermoelectric properties of material.