Enhancement of Thermoelectric Performance in Hierarchical Mesoscopic Oxide Composites of Ca₃Co₄O₉ and La_0.8Sr_0.2CoO₃

Abstract

The natural contradiction in enhancing electrical conductivity and thermopower in thermoelectric oxides makes it hard to improve the performance of a single thermoelectric oxide material. We report a facile method to construct a unique architecture of thermoelectric oxides that is promising to realize a simultaneous improvement of overall electrical conductivity and thermopower. Here, a series of two-phase nanocomposites comprising of Ca 3 Co 4 O 9 (CCO) and La 0.8 Sr 0.2 CoO 3 (LSCO) has been synthesized through ball milling followed by spark plasma sintering (SPS) method. The electron microscope images reveal that the two constituents form the unique composites while retaining their individual crystalline and morphological identities. Owing to the hierarchical mesoscopic structure with nanoscale particles and submicrometer scale grain boundaries, an external strain is induced into the CCO grains by the LSCO nanoparticles to enhance the thermopower. The mesoscopic structure is also favorable for improving the electrical conductivity. Moreover, the long-wavelength phonons can be scattered effectively from LSCO nanoparticles and the thermal conductivity is further suppressed. With compromises between power factor and thermal conductivity, the largest ZT achieved is up to 0.41 at 1000 K for the composites with 25 wt% of LSCO.

Realizing High Thermoelectric Performance in n‐Type Highly Distorted Sb‐Doped SnSe Microplates via Tuning High Electron Concentration and Inducing Intensive Crystal Defects

“…For the strategies of achieving high S 2 σ, resonant state doping, band converging, minority carrier blocking, and quantum confinement were designed and developed. For reducing κ, the strategies of nanostructuring, hierarchical architecturing, and nanoprecipitate inducing were successfully adopted.…”

“…[9] For the strategies of achieving high S 2 σ, resonant state doping, [10][11][12] band converging, [13][14][15][16] minority carrier blocking, [17,18] and quantum confinement [19][20][21] were designed and developed. For reducing κ, the strategies of nanostructuring, [22][23][24][25] hierarchical architecturing, [26][27][28] and nanoprecipitate inducing [29][30][31] were successfully adopted.Tin selenide (SnSe) is a typical semiconductor with a narrow bandgap of ≈0.9 eV, [32][33][34] making it a good candidate with great potentials for applications in low-cost thermoelectrics. [35][36][37] A remarkable high peak ZT of ≈2.6 at 923 K was reported in the p-type SnSe single crystals, [38] and a relative high ZT of ≈2.2 at 773 K was also achieved from the n-type Bi-doped SnSe single crystals, [39] both along their b-axes.…”

Pronounced effect of ZnTe nanoinclusions on thermoelectric properties of Cu2−x Se chalcogenides

“…Meanwhile, the thermoelectric efficiency has also been enhanced by using various techniques such as growth of nanowires [2,3], nanocomposites [1,4−6], superlattices [7] and thin films [8]. Bulk nanocomposites has also been reported to reduce thermal conductivity without affecting the electronic transport [5]. Presently, copper chalcogenides are getting more attention due to their simple chemical formula but complex crystal structures [9−12].…”

Composites between Perovskite and Layered Co-Based Oxides for Modification of the Thermoelectric Efficiency

“…Through rational manipulation of particle sizes and interfacial effects, it is possible to increase the power factor together with a reduction of the thermal conductivity, thus yielding the enhancement of the thermoelectric activity of composites in comparison with the individual constituents. Supporting this assumption, it has recently been found that hierarchical mesoscopic oxide composites of Ca 3 Co 4 O 9 and La 0.8 Sr 0.2 CoO 3 display enhanced thermopower [12]. However, the experimental observations of interfacial effects still remain elusive.…”