Modulation of electrical and thermal transports through lattice distortion in BaTi1 -xNbxO3solid solutions

Yuqiao Zhang; Hai Jun Cho; Feng Jiang; Chengliang Xia; Yue Chen; Weishu Liu; Hiromichi Ohta

doi:10.1088/1361-6528/ac78f3

Modulation of electrical and thermal transports through lattice distortion in BaTi_{1 -x}Nb_xO₃solid solutions

Nanotechnology. 2022 Jul 13;33(40). doi: 10.1088/1361-6528/ac78f3.

Authors

Yuqiao Zhang^{1

2

3}, Hai Jun Cho², Feng Jiang⁴, Chengliang Xia⁵, Yue Chen⁵, Weishu Liu⁴, Hiromichi Ohta²

Affiliations

¹ Institute of Quantum and Sustainable Technology (IQST), School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, People's Republic of China.
² Research Institute for Electronic Science, Hokkaido University, N20W10, Kita, Sapporo 001-0020, Japan.
³ Foshan (Southern China) Institute for New Materials, Foshan 528200, People's Republic of China.
⁴ Department of Materials Science and Engineering, Southern University and Science and Technology, Shenzhen 518055, People's Republic of China.
⁵ Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, People's Republic of China.

PMID: 35705009
DOI: 10.1088/1361-6528/ac78f3

Abstract

The electron and heat transports in solids are through the movement of carrier electrons and quantized lattice vibrations (phonons), which are sensitive to the lattice distortion and ionized impurities, and are essential aspects for the development of novel thermoelectric materials. In this study, we systematically investigated the modulations of electrical and thermal conductivities of BaTi_1-xNb_xO₃solid solution (BTNO, 0 ≤ x ≤ 1) epitaxial films. At room temperature, BaTiO₃belongs to tetragonal perovskite and exhibits electron conduction through doubly degenerated Ti 3d-t_2gorbitals upon doping, while BaNbO₃belongs to cubic perovskite and exhibits metallic electron conduction through partially filled triply degenerate Nb 4d-t_2gorbitals. By controlling the Ti/Nb ratio, we found a dual modulation effect on both the lattice structures and conduction band, which affects the electrical and thermal conductivities. Similar to the SrTi_1-xNb_xO₃solid solution (STNO, 0 ≤ x ≤ 1) system, a phase transition was detected atx ∼ 0.5, at which both the electron and heat transports exhibit abrupt changes. Unlike the transition in STNO, which was attributed to a polaronic phase transition, the transition in BTNO was due to contributions from both the lattice distortion and polaron effect. By controlling the lattice distortion, conduction band, and polaronic phase transitions, the electrical and thermal conductivity of BTNO epitaxial films are modulated within a much greater range than those of the STNO epitaxial films. Due to the double contribution of electron carriers and phonon to thermal conductivity (κ), the maximumκmodulation ratio of BTNO epitaxial films was ∼6.9. Our research provides an effective route to design electrical/thermal management materials.

Keywords: electrical conductivity; phase transition; thermal conductivity; thermoelectrics.