Selective Forming Process for Microstructures Engineering of BST-based Ceramics to Achieve Promoted Electrocaloric Performance

Ferroelectric electrocaloric (EC) materials are crucial for sustainable micro-cooling in miniaturized devices. However, the application of EC materials is largely limited by the unsatisfactory room-temperature EC response and narrow operation temperature window. In this work, interestingly, microstructures of Ba 0.75 Sr 0.25 TiO 3 based ceramics can be tailored by optimized forming methods, such as uniaxial pressing (UP), cold isostatic pressing (CIP), and CIP combined with oxygen annealing (CIP@O 2 ). With the delicate modifications, the electrocaloric temperature change ( ΔT ) of > 0.50 K was achieved in a broaden temperature ranging from 15 °C to 100 °C. Moreover, a peak ΔT value of 1.30 K was obtained at temperature of 70 °C in Ba 0.75 Sr 0.25 Zr x (Mn 0.001 Ti 0.999 ) 1- x O 3 (BSZMT) with x = 0.05 (CIP@O 2 ). The CIP@O 2 method can effectively modulate the phase fraction of BSZMT with an orthorhombic-tetragonal phase coexistence and dynamic polar nanoregions. Therefore, the EC performance and wide operating temperature range are obtained in lead-free ferroelectric ceramics.