Phase transition of Eu 2 Ti 2 O 7 under high pressure and a new ferroelectric phase with perovskite‐like layered structure

Ferroelectrics with perovskite‐like layered (PL) structure are well‐known for their high T c and the application prospect of high‐temperature‐piezoelectric sensing. In this study, the PL‐structure Eu 2 Ti 2 O 7 was prepared by 1‐step high‐pressure sintering, which show the pyrochlore structure of Eu 2 Ti 2 O 7 would change into PL structure at 11 GPa, 1300°C. The PL‐structure Eu 2 Ti 2 O 7 is metastable, which will change back to pyrochlore structure at about 900°C in the air. The PL‐structure Eu 2 Ti 2 O 7 was confirmed as a high‐temperature ferroelectric material for the first time. The ferroelectric domain switching was directly observed using piezoelectric force microscope. The piezoelectric constant of the PL Eu 2 Ti 2 O 7 ceramic was measured as 0.7‐0.9 pC/N and its thermal depoling temperature ( T d ) was determined as 800°C, which is associated with the PL‐pyrochlore transition.