Ca_3Co_4O_9陶瓷的热传输特性(英文)

THERMAL TRANSPORT PROPERTIES OF Ca_3Co_4O_9 CERAMICS

采用溶胶-凝胶法,结合常压烧结工艺制备了Ca_3Co_4O_9陶瓷。通过热重-差示扫描量热法(thermogravimetric-differential scanning calorimetry, TG-DSC)、X射线衍射(X-ray diffraction,XRD)和扫描电镜(scanning electron microscope,SEM)等测试手段探讨了Ca_3Co_4O_9陶瓷的形成过程,分析了不同工艺参数对Ca_3Co_4O_9陶瓷显微结构及性能的影响,研究了晶粒尺寸与热传输性能之间的关系。结果显示:Ca_3Co_4O_9为取向无规则层片状结构,当煅烧温度为750～900℃时,能得到纯相Ca_3Co_4O_9。Ca_3Co_4O_9陶瓷的热导率(κ)较低,且随着温度的升高而逐渐增大。晶粒尺寸的减小对其晶格热导率(κ_1)影响显著,当平均晶粒由92 nm减小到63 nm时,κ_1由1.529W/(m·K)减小到0 959W/(m·K),但对载流子热导率(κ_c)的影响很小。Ca_3Co_4O_9陶瓷的κ随晶粒尺寸的减小而降低,主要是由于κ_1随晶粒尺寸的减小而降低所致。

Calcium cobaltite ceramics were prepared by the sol-gel method combined with the ordinary pressing sintering. The pyrolytic decomposition mechanism of the dried gel, formation process and the microstructures of Ca3Co4O9 ceramics were investigated by the thermogravimetric-differential scanning calorimetry （TG-DSC）, X-ray diffraction（XRD） and scanning electron microscope（SEM）. The influence of different technical parameters on the microstructure and properties of the ceramics were analyzed. The influence of crystal grain sizes on the thermal transport properties of Ca3Co4O9 ceramics was investigated systematically. The results show single phase Ca3Co4O9 can be fabricated at 750-900℃. Ca3Co4O9 ceramics contain randomly-oriented plate-shaped grains with a layered structure. The thermal conductivities （K） are low, and increase with the increase of temperature. The lattice thermal conductivity （K1） falls remarkably when the grain sizes of the Ca3Co4O9 ceramics decrease. When the grain sizes decrease from 92 nm to 63 nm, the Xl decreases from 1.529 W/（m·K） to 0.959W/（m·K）, while the cartier thermal conductivity （Kc） decreases less drastically with the decrease of grain size. The decrease in the K of Ca3Co4O9 ceramics with the decrease of grain size is mainly due to the reduction in the K1.