High-Entropy Perovskites: An Emergent Class of Oxide Thermoelectrics with Ultralow Thermal Conductivity

Abstract

Although SrTiO3-based perovskites showed a lot of promise as n-type thermoelectric (TE) materials, they demonstrated a low figure of merit value primarily because of their high lattice thermal conductivity (k l). Researchers found it difficult to reduce k l, as a popular route like nanostructuring did not work well with these perovskites possessing low phonon mean free paths. Here, we put forward a novel strategy of designing high-entropy perovskite (HEP) oxides having five transition metals in the B site to induce more anharmonicity causing enhanced multiphonon scattering in order to decrease k l. Using detailed thermodynamic calculations, we designed and synthesized a highly dense Sr­(Ti0.2Fe0.2Mo0.2Nb0.2Cr0.2)­O3 HEP ceramic. An ultralow thermal conductivity of 0.7 W/mK at 1100 K was achieved in this n-type rare-earth-free HEP oxide TE material. The concept of designing HEPs to achieve ultralow thermal conductivity potentially opens up a new avenue for enhancing TE performance of environmentally benign bulk oxides for high-temperature TE power generation.

Synthesis and characterizations of (Mg, Co, Ni, Cu, Zn)O high-entropy oxides

“…A study by Edalati et al [29] on the photocatalytic properties of HEOs for hydrogen evolution, on the other hand, showed an appreciable light absorbance in the visible-light region for water splitting. Bérardan et al [30] also reported that HEOs can exhibit colossal dielectric constant for applications as large-k dielectric materials. Moreover, Wang et al [31] studied HEOs for applications as anode materials for Li-ion batteries.…”

Selective Enhancement in Phonon Scattering Leads to a High Thermoelectric Figure-of-Merit in Graphene Oxide-Encapsulated ZnO Nanocomposites

“…This fitting is used to extract the various contributions of phonon scattering. According to this model, the lattice thermal conductivity is given as 9,16…”

“…which shows zT of more than one and the next generation materials having zT of even about two 3,8 . These are even used in commercial devices however the mere fact that they contain elements like Bi, Te, Sb, Pb etc which are toxic and less earth abundant, demands the scientific community to search for new earth abundant and high TE efficiency materials 9,10 . In order to overcome the severe problem of environmental hazards of these materials and low abundance, drove a strong push for exploring earth abundant elements and particularly benign oxides.…”

“…Therefore, enhancement in the PF and reduction in thermal conductivity are the key to achieve a high value for the TE efficiency of a material . A large number of chemical compositions have been explored for a high zT from alloys to oxides and even polymers. , There are a few highly efficient TE materials such as Bi 2 Te 3 , PbTe, and so forth, which shows zT of more than one and the next-generation materials having zT of even about two. ,, These are even used in commercial devices; however, the mere fact that they contain elements such as Bi, Te, Sb, Pb, and so forth, which are toxic and less earth-abundant, demands the scientific community to search for new earth-abundant and high-TE efficiency materials. , To overcome the severe problem of environmental hazards of these materials and low abundance, there is a strong​ need for exploring earth-abundant elements. Particularly benign oxides, because oxides are thermally as well as chemically stable and are easier to synthesize compared to alloys …”

High-entropy oxides for the oxygen evolution reaction

“…[8][9][10][11] High-entropy oxides (HEOs) are oxides consisting of five or more metals in addition to oxygen. [12] Since the first characterisation of a HEO in 2015, [13] these materials have been investigated for their distinct thermal, magnetic and electrochemical properties, [14][15][16][17] and furthermore inspired the development of other multi-component ceramic materials. [18] Thermodynamically, HEOs are analogous to high-entropy alloys (HEAs) in that the configurational entropy, arising from the many possible arrangements of the different elements, plays an important role in the thermodynamic stability of the materials.…”