Nanoscale heterogeneity in thermoelectrics: the occurrence of phase separation in Fe-doped Ca3Co4O9
- Resource Type
- Authors
- Jinle Lan; Wei Xu; Yingcai Zhu; Ce-Wen Nan; Augusto Marcelli; Meijuan Yu; Jing Zhou; Yong Liu; Yuanhua Lin; Sajid Butt
- Source
- Physical Chemistry Chemical Physics. 18:14580-14587
- Subject
- Materials science
Condensed matter physics
Absorption spectroscopy
Doping
General Physics and Astronomy
Mineralogy
02 engineering and technology
Electronic structure
010402 general chemistry
021001 nanoscience & nanotechnology
Thermoelectric materials
01 natural sciences
XANES
0104 chemical sciences
Thermoelectric effect
Slab
Density functional theory
Physical and Theoretical Chemistry
0210 nano-technology
- Language
- ISSN
- 1463-9084
1463-9076
The misfit layered cobaltate thermoelectrics are good candidates for high temperature thermoelectric applications. Ca3Co4O9 is a typical compound of this family, which consists of rock salt Ca2CoO3 slabs alternating with hexagonal CoO2 slabs with a large lattice mismatch along the b axis. Each slab is 0.3-0.5 nm thick and shows an inherent structural heterogeneity at the nanoscale. The latter is a key parameter that affects the electrical transport and the heat flow in these misfit structured thermoelectrics. To clarify the physical origin of the thermoelectric performance of iron doped Ca3Co4O9 we combined X-ray near-edge absorption spectroscopy (XANES) and quantum modeling using density functional theory. In contrast to single-site doping, the iron doping first occurs at the Co1 site of the rock salt slab at low doping while at higher doping it prefers the Ca1 site of the rock salt slab. Doping at the Ca1 site modifies the electronic structure tuning the nanoscale structural heterogeneity. This mechanism may open a new route to optimizing the thermoelectric performance of misfit layered thermoelectrics.