Seeing Structural Mechanisms of Optimized Piezoelectric and Thermoelectric Bulk Materials through Structural Defect Engineering

Abstract

Aberration-corrected scanning transmission electron microscopy (AC-STEM) has evolved into the most powerful characterization and manufacturing platform for all materials, especially functional materials with complex structural characteristics that respond dynamically to external fields. It has become possible to directly observe and tune all kinds of defects, including those at the crucial atomic scale. In-depth understanding and technically tailoring structural defects will be of great significance for revealing the structure-performance relation of existing high-property materials, as well as for foreseeing paths to the design of high-performance materials. Insights would be gained from piezoelectrics and thermoelectrics, two representative functional materials. A general strategy is highlighted for optimizing these functional materials’ properties, namely defect engineering at the atomic scale.

Regulating the Configurational Entropy to Improve the Thermoelectric Properties of (GeTe)1−x(MnZnCdTe3)x Alloys

“…The energy conversion efficiency of the TE device is determined by the component materials’ dimensionless figure of merit, zT = α 2 σT / κ , where T , α , σ and κ denote the absolute temperature, Seebeck coefficient, electrical conductivity and thermal conductivity (including carrier component κ e and lattice component κ L ), respectively [ 3 ]. Aiming at decoupling the adversely interdependent TE parameters { α , σ , κ } and thus the high zT , the band engineering [ 4 , 5 , 6 ] and microstructure engineering [ 7 , 8 , 9 , 10 , 11 ] are implemented to enhance the power factor PF = σα 2 and reduce the κ L , simultaneously. For TE materials undergoing phase transition, implementing phase engineering can also expand the phase favorable to thermoelectric and restrain the negative phase [ 12 , 13 ].…”