采用溶胶-凝胶法制备Ca((2.7)M_(0.3)Co_4O_9(M=Ag~+,Sr~(2+),Yb~(3+_)系列陶瓷样品,通过XRD和SEM对样品结构进行表征,考察了掺杂对材料电阻率和Seebeck系数的影响.陶瓷样品XRD图呈现出尖锐的(00l)相,且断面形貌呈片层状,说明压片烧结使样品内部晶粒择优取向,形成高度织构.Ag~+掺杂使电阻率略有下降.Sr~(2+)掺杂使电阻率明显降低,提高了功率因子在850K时达到2.62×10!~(-4)W/(m-1·K~(-2)).Yb~(3+)掺杂使Seebeck系数明显提高,但同时也增加了电阻率.因此,在相同掺杂量下,Ca_(2.7)Sr_(0.3)Co_4O_9为优化载流子(空穴)浓度的最佳值.
A series of ceramic samples Ca_(2.7)M_(0.3)Co_4O_9(M=Ag~+,Sr~(2+),Yb~(3+)) were prepared by sol-gel method.The structures were characterized with XRD and SEM.The effect of doping on electrical resistivity and Seebeck coefficient was studied.The sharp (00l) phase of XRD diagram of ceramic block declared the formation of a high degree of texture and the layered grain preferred orientation along the pressure direction.The morphology of cross section displayed a lamellar and dense structure.Ag~+-doping decreased electrical resistivity.Sr~(2+)-doping decreased the electrical resistivity significantly and improved the power factor to 2.62×10~(-4)W/(m·K~2) at 800K.Yb~(3+)-doping made the Seebeck coefficient markedly improved,but also increased the electrical resistivity.Therefore,in the same amount of doping,Ca_(2.7)Sr_(0.3)Co_4O_9 was the best value to optimize the carrier (hole) concentration.
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