High Power Factor Nb-Doped TiO2 Thermoelectric Thick Films: Toward Atomic Scale Defect Engineering of Crystallographic Shear Structures

TY - JOUR

T1 - High Power Factor Nb-Doped TiO2 Thermoelectric Thick Films

T2 - Toward Atomic Scale Defect Engineering of Crystallographic Shear Structures

AU - Liu, Xiaodong

AU - Kepaptsoglou, Demie

AU - Jakubczyk, Ewa

AU - Yu, Jincheng

AU - Thomas, Andrew

AU - Wang, Bing

AU - Azough, Feridoon

AU - Gao, Zhaohe

AU - Zhong, Xiangli

AU - Dorey, Robert

AU - Ramasse, Quentin M

AU - Freer, Robert

N1 - © 2023 The Authors.

PY - 2023/1/19

Y1 - 2023/1/19

N2 - Donor-doped TiO 2-based materials are promising thermoelectrics (TEs) due to their low cost and high stability at elevated temperatures. Herein, high-performance Nb-doped TiO 2 thick films are fabricated by facile and scalable screen-printing techniques. Enhanced TE performance has been achieved by forming high-density crystallographic shear (CS) structures. All films exhibit the same matrix rutile structure but contain different nano-sized defect structures. Typically, in films with low Nb content, high concentrations of oxygen-deficient {121} CS planes are formed, while in films with high Nb content, a high density of twin boundaries are found. Through the use of strongly reducing atmospheres, a novel Al-segregated {210} CS structure is formed in films with higher Nb content. By advanced aberration-corrected scanning transmission electron microscopy techniques, we reveal the nature of the {210} CS structure at the nano-scale. These CS structures contain abundant oxygen vacancies and are believed to enable energy-filtering effects, leading to simultaneous enhancement of both the electrical conductivity and Seebeck coefficients. The optimized films exhibit a maximum power factor of 4.3 × 10 -4 W m -1 K -2 at 673 K, the highest value for TiO 2-based TE films at elevated temperatures. Our modulation strategy based on microstructure modification provides a novel route for atomic-level defect engineering which should guide the development of other TE materials.

AB - Donor-doped TiO 2-based materials are promising thermoelectrics (TEs) due to their low cost and high stability at elevated temperatures. Herein, high-performance Nb-doped TiO 2 thick films are fabricated by facile and scalable screen-printing techniques. Enhanced TE performance has been achieved by forming high-density crystallographic shear (CS) structures. All films exhibit the same matrix rutile structure but contain different nano-sized defect structures. Typically, in films with low Nb content, high concentrations of oxygen-deficient {121} CS planes are formed, while in films with high Nb content, a high density of twin boundaries are found. Through the use of strongly reducing atmospheres, a novel Al-segregated {210} CS structure is formed in films with higher Nb content. By advanced aberration-corrected scanning transmission electron microscopy techniques, we reveal the nature of the {210} CS structure at the nano-scale. These CS structures contain abundant oxygen vacancies and are believed to enable energy-filtering effects, leading to simultaneous enhancement of both the electrical conductivity and Seebeck coefficients. The optimized films exhibit a maximum power factor of 4.3 × 10 -4 W m -1 K -2 at 673 K, the highest value for TiO 2-based TE films at elevated temperatures. Our modulation strategy based on microstructure modification provides a novel route for atomic-level defect engineering which should guide the development of other TE materials.

U2 - 10.1021/acsami.2c16587

DO - 10.1021/acsami.2c16587

M3 - Article

C2 - 36656149

SN - 1944-8244

JO - ACS applied materials & interfaces

JF - ACS applied materials & interfaces

ER -