Re-entrant relaxor–ferroelectric composite showing exceptional electromechanical properties

Thermal stability, precision, and large output are desired for applications of electromechanical materials. However, this combination has been hardly attained because both the commercially used materials and currently promising candidates are confronted with a critical challenge: the intrinsic incompatibility among the broad temperature window, low hysteresis, and high strain. Here we report a re-entrant relaxor–ferroelectric composite that solves this long-standing challenge: a combination of low hysteresis and large electrostrain over a broad temperature range (i.e., a 168-K temperature window for hysteresis <20% and strain >0.1%) in sufficiently disordered (Ba0.925Bi0.05)(Ti1−x/100Snx/100)O3 ceramics. In situ transmission electron microscopic observations and permittivity measurements reveal the existence of a re-entrant anomaly that guarantees the relaxor–ferroelectric microstructure over a broad temperature range and the resulting combination of exceptional properties. Our finding of a re-entrant relaxor–ferroelectric composite not only solves the incompatibility of the electromechanical properties but may also open a way to develop thermally stable high-performance materials. This work first reports the finding of a re-entrant relaxor–ferroelectric composite (RRFC) which solves a long-standing challenge: a combination of low hysteresis and large electrostrain over a broad temperature range (i.e., 168 K temperature window for hysteresis <20% and strain >0.1%) in sufficiently disordered (Ba0.925Bi0.05)(Ti1−x/100Snx/100)O3 ceramics. This exceptional combination is achieved by the RRFC designing strategy; i.e., introducing sufficient disorder to enable a re-entrant transition and thereby creating a relaxor–ferroelectric coexisting microstructure over a broad temperature range. Our finding does not only solve the incompatibility of electromechanical properties but also may open a way to develop thermally stable high-performance materials. Deliberately introducing disorder into ceramics that alter their shape when stimulated by electricity may lead to new cold-temperature applications. Ceramics that use electrically guided movements to manipulate imaging and sensing devices can become unresponsive when cold because of the formation of stable crystal states. Researchers led by Yuanchao Ji at China’s Xi’an Jiaotong University and Xiaobing Ren from the National Institute for Materials Science in Tsukuba, Japan have developed a barium-based material that avoids these immobile states thanks to its unusual microstructure. The team found that adding small amounts of bismuth and tin to the ceramic created random “nanoregions” of electric dipoles at low temperatures. These tiny zones interfere with typical thermodynamic transitions and enable the ceramic to undergo repeated movements at temperatures ranging from sub-zero to over 100 °C.