关键词: 双掺杂, 溶胶-凝胶法, 热电性能, 陶瓷材料

Abstract:

A series of ceramic materials, Ca_3-x-yAg_xSr_yCo₄O_9-δ, Ca_3-x-zAg_xYb_zCo₄O_9-δ and Ca_3-y-zSr_yYb_zCo₄O_9-δ(x, y, z=0.1, 0.15, 0.2) which worked from 300 K to 870 K with excellent thermoelectric properties, was prepared by sol-gel and cold-pressing method. The XRD, IR and SEM results reveal that the prepared samples are uniform crystal particles with high purity. Ag⁺, Sr²⁺ and Yb³⁺ ions have replaced the position of Ca²⁺ ions and they are dissolved in the crystal, which changes the cell volume of the dual-doping materials but does not change the crystal symmetric structure. The characterization results of resistivity and Seebeck coefficient reveal that the concentration of carrier is optimized by dual doping, accordingly the resistivity decreases continuously with the doped different materials and the value of Seebeck coefficient increases continuously with the doped different materials. It can be concluded from the calculations that the electron effective mass contributes to the increase of Seebeck coefficient. The characterization results of thermal conductivity indicate that the thermal conductivity of dual doped samples decreases with the increase of temperature, and the phonon thermal conductivity still contributes more in the prepared system, which is consistent with the results of Ag⁺, Sr²⁺, Yb³⁺ single doped Ca₃Co₄O_9-δ samples. The figure of metrt ZT of Ca_2.7Ag_0.2Yb_0.1Co₄O_9-δ exceeds 0.18 at 870 K.

Key words: Dual doping, Sol-gel process, Thermoelectric property, Ceramics