Organic ferroelastic enantiomers with high Tc and large dielectric switching ratio triggered by order-disorder and displacive phase transition

Molecular-based ferroelastics with dielectric switching properties are highly desirable for their applications on microelectronic dielectric switches,sensors,data storage,and so on.However,the current reports mostly focus on organic-inorganic hybrids containing toxic heavy metal atoms,and the relatively low phase transition temperature limits their application.In this paper,low-toxic organic salt ferroelastic enantiomers(R/S)-4-fluoro-1-azabicyclo[3.2.1]octonium chloride[(R/S)-F-321]were designed and synthesized under the introducing chirality strategy.They undergo a 432F422-type ferroelastic phase transition with a high Curie temperature(Tc)of 470 K,simultaneously exhibiting excellent dielectric switching characteristics.In addition to the ordered-disordered movement of cations,the significant displacement of anions is also responsible for such high Tc and large dielectric switching ratios,which is very rare in molecular-based switching materials.This work enriches the development of molecular ferroelastic switching materials and gives inspiration for the exploration of environmentally friendly high Tc organic salt ferroelastics with prominent switching performances.