Converting Brownmillerite to Alternate Layers of Oxygen‐Deficient and Conductive Nano‐Sheets with Enhanced Thermoelectric Properties

Abstract Introducing large oxygen deficiencies while retaining low resistivity is important for enhancing the overall thermoelectric properties in 3d transition‐metal oxides. In this study, a new synthesis route to reconstruct insulating brownmillerite SrCoO 2.5 adapted. Through step‐by‐step nano‐blocks modification, series of highly‐conductive layered structures evolved, which are [Sr 2 O H ] 0.5 CoO , 0.4 and 3 0.57 still considerable Seebeck coefficient ( ≈ 100 µ V K −1 ). Coexistence high deficiency realized latter two polymorphs by forming majority sintered vacancies rock‐salt layer minority normal layer. A room‐temperature in‐plane power factor 3.6 mW −2 m output density 4.5 W at temperature difference 28 K, an out‐of‐plane thermal conductivity 0.33 obtained thin film that exhibits highest (δ = 2.95), on par with Bi Te benchmark. It pointed out proper distribution vacancy essential tailoring physical chemical The sintered/normal model provides guidance exploration materials both electric conductivity.