مقاله انگلیسی دستیابی به افزایش عملکرد ترموالکتریک Ca1 − x − yLaxSryMnO3
Highlights
Abstract
Graphical abstract
Keywords
1. Introduction
2. Methods
3. Results and discussion
4. Conclusion
Declaration of Competing Interest
Acknowledgements
Appendix A. Supplementary data
References
Abstract
In this work, we fabricate perovskite-type Ca1−x−yLaxSryMnO3 thermoelectric materials using co-precipitation method, followed by cold pressing and hot sintering. The La/Sr dual doping modifies chemical composition and bonding properties of CaMnO3, resulting in improved electrical transport properties with tunable carrier concentration, carrier mobility and effective mass. Meanwhile, the phonon transport properties are also influenced, reflected by the reduced lattice thermal conductivity of Ca1−x−yLaxSryMnO3. As a result, Ca0.94La0.02Sr0.04MnO3 shows significantly enhanced power factor up to 374 μW·m−1·K−2 and figure of merit up to ~0.22 at 973 K, which is ~144% higher than those of pristine CaMnO3. This study rationalizes a potential strategy to improve the thermoelectric performance of CaMnO3-based materials.
1. Introduction
The increasing consumption of fossil fuels and the deteriorating environmental pollution have driven researchers to explore alternative and sustainable energy-supply technologies [1-3]. Thermoelectric materials and devices enable the direct conversion between heat and electricity [4], showing great potential in improving energy efficiency and recovering waste heat from diverse heat sources. Their conversion efficiency is dominated by the dimensionless figure-of-merit (zT) [5-8], defined as zT = S 2σT/κ, where S, σ, κ and T are the Seebeck coefficient, electrical conductivity, thermal conductivity and absolute temperature, respectively. Accordingly, an ideal thermoelectric material relies on a large power factor (PF = S2σ) and a low κ, while PF and κ are strongly coupled by the carrier concentration (n).
Currently, thermoelectric materials with zT values exceeding 1 have been extensively obtained [3, 9-15]. However, the high cost, instability in air atmosphere or toxicity may limit their applications [16-18]. Oxides-based thermoelectric ceramics with advantages of chemical and structural stability, low cost and low toxicity have been regarded as potential thermoelectric materials for applications above 800 K [19, 20]. As one of the promising candidates, n-type perovskite CaMnO3 with intrinsically high |S| (550 μV K-1 at room temperature) has received much interest due to its unique structure, magnetic and topological properties [21-30]. However, its high electrical resistivity () and κ lead to low zT values. Previous studies have revealed that the substitutions of trivalent rare earth elements such as La, Ce or Pr on the Ca-site of CaMnO3 can simultaneously reduce and κ, along with a moderate decrease of |S| [31- 33]. Moreover, theoretical calculations [34, 35] indicate that Sr-doping can contribute to larger effective mass of carriers (m*), enhanced density of states (DOS) near the Fermi level, and complicated phonon frequency modes, which is essential to optimize the thermoelectric parameters of CaMnO3. Therefore, applying a dual doping strategy of rare earth elements and Sr on CaMnO3 could be a key to achieve synergistically improved thermoelectric properties.