On the origin of enhanced thermoelectricity in Fe doped Ca sub(3)Co sub(4)O sub(9)

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 1; no. 26; pp. 4114 - 4121
• Main Authors: Wu, Tao, Tyson, Trevor A, Bai, Jianming, Pandya, Kaumudi, Jaye, Cherno, Fischer, Daniel
• Format: Journal Article
• Language: English
• Published: 01.06.2013
• Subjects: Blocking; Coefficients; Diffraction; Doping; Electrical resistivity; Iron; Thermoelectricity; X-rays
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c3tc30481g

Resistivity and Seebeck coefficient measurements on Ca sub(3)Co sub(4-x)Fe sub(x)O sub(9) (x= 0, 0.05, 0.1, 0.2 and 0.25) reveal enhanced thermoelectric performance with an optimal x value of 0.2. X-ray diffraction measurements show continuous Fe doping into the host lattice, while X-ray absorption experiments reveal that Fe substitutes for Co in the Ca sub(2)CoO sub(3) (rock salt) block. The Fe substitution for Co produces electron doping. The local structure around Fe in the Ca sub(2)CoO sub(3) block becomes disordered, while the structure in the conducting CoO sub(2) layer becomes more ordered. The structural change in the CoO sub(2) layer plays the key role to enhance the electron transport. The highest ordered structure is achieved at x= 0.2 with the lowest resistivity. Soft X-ray absorption measurements find no Co site spin-state change with Fe doping. Thermoelectric property enhancement associated with doping induced structural change points to a new approach for creating materials with improved ZT in complex oxide systems.